Disable the secondary texcache on mobile.

It helps in games like Final Fantasy 2 and Popolocrois, but it seems to
cause out of memory errors despite the checks.
Rewrite QuickTexHashNEON directly in asm.

Seems like gcc couldn't optimize it to this.
Handcode the non-NEON texcache hash as well on ARM.

Well, it could be a better algorithm, but at least this uses LDMIA.
Merge pull request #4487 from unknownbrackets/perf

Texture cache hashing tweaks, disable second cache on mobile