armv8: Remove duplicate definition for IH_ARCH_ARM and IH_ARCH_ARM64

The duplicate definitions for IH_ARCH_ARM and IH_ARCH_ARM64 are removed.
The definitions in <image.h> are used.

According to this modification, the comparison between os arch and cpu
arch is done in C programming instead of ASM programming.

Signed-off-by: Alison Wang <alison.wang@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>