Use the compiler for endian conversions
Use the compiler for endian conversions

clang and gcc both define macros describing the endianess of the target
architecture and have builtin macros for byte swapping. The macros
expand in place and lets the compiler insert specialised assembly if it
so chooses.

Change-Id: I6060a0a7952f0863797db65d471f1d21c215b671

project-oak/hafnium-verification,project-oak/hafnium-verification,project-oak/hafnium-verification,project-oak/hafnium-verification,project-oak/hafnium-verification,project-oak/hafnium-verification,project-oak/hafnium-verification