arm: Finish migration of CONFIG_MACH_TYPE

As this is only useful when booting with ATAGs, which are now largely
disabled, remove this value for the remaining platforms.  We have a few
places in the code that had been testing for MACH_TYPE as a sort of
internal logic.  Update those to use different but still correct CONFIG
symbols.

Cc: Phil Sutter <phil@nwl.cc>
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/axm_defconfig b/configs/axm_defconfig
index eae53eb..a013338 100644
--- a/configs/axm_defconfig
+++ b/configs/axm_defconfig
@@ -28,7 +28,7 @@
 CONFIG_SPL_SPI=y
 CONFIG_DEBUG_UART=y
 CONFIG_SYS_LOAD_ADDR=0x22000000
-CONFIG_SYS_EXTRA_OPTIONS="AT91SAM9G20,MACH_TYPE=2068"
+CONFIG_SYS_EXTRA_OPTIONS="AT91SAM9G20"
 CONFIG_BOOTDELAY=3
 CONFIG_USE_BOOTCOMMAND=y
 CONFIG_BOOTCOMMAND="run flash_self"