arm: Re-sync ARCH_MX5 / MX51 / MX53 CONFIG options

A few boards had not been fully re-synced with CONFIG_ARCH_MX5 / CONFIG_MX51 /
CONFIG_MX53 being in Kconfig.  Do so now.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/mx51evk_defconfig b/configs/mx51evk_defconfig
index 9ac4b65..b385009 100644
--- a/configs/mx51evk_defconfig
+++ b/configs/mx51evk_defconfig
@@ -1,4 +1,5 @@
 CONFIG_ARM=y
+CONFIG_ARCH_MX5=y
 CONFIG_TARGET_MX51EVK=y
 CONFIG_VIDEO=y
 CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=board/freescale/mx51evk/imximage.cfg"