Create a new boot/ directory

Quite a lot of the code in common/relates to booting and images. Before
adding more it seems like a good time to move the code into its own
directory.

Most files with 'boot' or 'image' in them are moved, except:

- autoboot.c which relates to U-Boot automatically running a script
- bootstage.c which relates to U-Boot timing

Drop the removal of boot* files from the output directory, since this
interfers with the symlinks created by tools and there does not appear
to be any such file from my brief testing.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Artem Lapkin <email2tema@gmail.com>
Tested-by: Artem Lapkin <email2tema@gmail.com>
diff --git a/scripts/Makefile.spl b/scripts/Makefile.spl
index 1bb2844..83a95ee 100644
--- a/scripts/Makefile.spl
+++ b/scripts/Makefile.spl
@@ -92,10 +92,10 @@
 
 # Special handling for a few options which support SPL/TPL
 ifeq ($(CONFIG_TPL_BUILD),y)
-libs-$(CONFIG_TPL_LIBCOMMON_SUPPORT) += common/ cmd/ env/
+libs-$(CONFIG_TPL_LIBCOMMON_SUPPORT) += boot/ common/ cmd/ env/
 libs-$(CONFIG_TPL_LIBGENERIC_SUPPORT) += lib/
 else
-libs-$(CONFIG_SPL_LIBCOMMON_SUPPORT) += common/ cmd/ env/
+libs-$(CONFIG_SPL_LIBCOMMON_SUPPORT) += boot/ common/ cmd/ env/
 libs-$(CONFIG_SPL_LIBGENERIC_SUPPORT) += lib/
 ifdef CONFIG_SPL_FRAMEWORK
 libs-$(CONFIG_PARTITIONS) += disk/