bootstd: Rename distro and syslinux to extlinux

We use the terms 'distro' to mean extlinux but they are not really the
same. 'Distro' could refer to any method of booting a distribution,
whereas extlinux is a particular method.

Also we sometimes use syslinux, but it is better to use the same term in
all cases.

Rename distro to syslinux and also update bootstd uses of syslinux to use
extlinux instead.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/usage/cmd/bootflow.rst b/doc/usage/cmd/bootflow.rst
index cad09bb..8590efc 100644
--- a/doc/usage/cmd/bootflow.rst
+++ b/doc/usage/cmd/bootflow.rst
@@ -148,7 +148,7 @@
 Device     mmc\@7e202000.bootdev
 Block dev  mmc\@7e202000.blk
 Type       distro
-Method:    syslinux
+Method:    extlinux
 State      ready
 Partition  2
 Subdir     (none)
diff --git a/doc/usage/cmd/bootmeth.rst b/doc/usage/cmd/bootmeth.rst
index 29d8215..f632d74 100644
--- a/doc/usage/cmd/bootmeth.rst
+++ b/doc/usage/cmd/bootmeth.rst
@@ -45,7 +45,7 @@
 =====  ===  ==================  =================================
 Order  Seq  Name                Description
 =====  ===  ==================  =================================
-    0    0  distro              Syslinux boot from a block device
+    0    0  extlinunx           Extlinux boot from a block device
     1    1  efi                 EFI boot from an .efi file
     2    2  pxe                 PXE boot from a network device
     3    3  sandbox             Sandbox boot for testing
@@ -77,7 +77,7 @@
     => bootmeth list
     Order  Seq  Name                Description
     -----  ---  ------------------  ------------------
-        0    0  distro              Syslinux boot from a block device
+        0    0  distro              Extlinux boot from a block device
         1    1  efi                 EFI boot from an .efi file
         2    2  pxe                 PXE boot from a network device
         3    3  sandbox             Sandbox boot for testing
@@ -92,7 +92,7 @@
     Order  Seq  Name                Description
     -----  ---  ------------------  ------------------
         0    3  sandbox             Sandbox boot for testing
-        1    0  distro              Syslinux boot from a block device
+        1    0  distro              Extlinux boot from a block device
     -----  ---  ------------------  ------------------
     (2 bootmeths)
 
@@ -102,7 +102,7 @@
     => bootmeth list -a
     Order  Seq  Name                Description
     -----  ---  ------------------  ------------------
-        1    0  distro              Syslinux boot from a block device
+        1    0  distro              Extlinux boot from a block device
         -    1  efi                 EFI boot from an .efi file
         -    2  pxe                 PXE boot from a network device
         0    3  sandbox             Sandbox boot for testing
diff --git a/doc/usage/cmd/dm.rst b/doc/usage/cmd/dm.rst
index 236cd02..74c6b01 100644
--- a/doc/usage/cmd/dm.rst
+++ b/doc/usage/cmd/dm.rst
@@ -366,7 +366,7 @@
     ..
     sysreset      0  [   ]   sysreset_sandbox      |-- sysreset_sandbox
     bootstd       0  [   ]   bootstd_drv           |-- bootstd
-    bootmeth      0  [   ]   bootmeth_distro       |   |-- syslinux
+    bootmeth      0  [   ]   bootmeth_extlinux     |   |-- extlinux
     bootmeth      1  [   ]   bootmeth_efi          |   `-- efi
     reboot-mod    0  [   ]   reboot-mode-gpio      |-- reboot-mode0
     reboot-mod    1  [   ]   reboot-mode-rtc       |-- reboot-mode@14