ARMv6 ISA has several instructions to handle data in different byte order.
For endian conversion (byte swapping) of single data words, it might be a
good idea to use the REV/REV16 instruction simply.
(git cherry-pick -e aa35095517)
Change-Id: Id6cca2e5e0a978f5abbee6d48876dfa8fa198f6a
