ARM: asm: Add ARM_BE8() assembly helper

ARM: asm: Add ARM_BE8() assembly helper

Add ARM_BE8() helper to wrap any code conditional on being
compile when CONFIG_ARM_ENDIAN_BE8 is selected and convert
existing places where this is to use it.

Acked-by: Nicolas Pitre <nico@linaro.org>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
(cherry picked from commit 457c2403c513c74f60d5757fd11ae927e5554a38)

Signed-off-by: Victor Kamensky <victor.kamensky@linaro.org>