Removes ARMv7 specific byteswap routines from CommonFuncs.h

GCC has optimized this using the exact same code since 4.7 or 4.8.
Android building falls back to the __linux__ route.
No need to keep these around anymore since we aren't building on an old GCC version.
Merge pull request #1389 from Sonicadvance1/remove-armv7-opt

Removes ARMv7 specific byteswap routines from CommonFuncs.h