vertexjit: Fix some stupid mistakes in x86 morph.

Good to have somewhere to test it properly.
vertexjit: Fix Jit_WriteMorphColor() on ARM.

It was totally wrong.
vertexjit: Fix dumb mistakes in NEON color morphs.
armjit: Use prefixes on vscl's T arg.

Makes it pass one more thing in the prefixes test, but not sure exactly
how it operates.  Better to have it the same as x86 and int anyway.
Merge pull request #5753 from unknownbrackets/vertexjit

Fix some color morph issues