[r300] Fix KIL instruction and swizzling of texture coordinates

[r300] Fix KIL instruction and swizzling of texture coordinates

The KIL instruction only works if at least one texture unit is enabled
in hardware.

Texture instructions do not support swizzles, negations etc. natively,
so we now emit an explicit swizzling etc. operation when the texture coordinate
requires it.

This fixes the Piglit fp-kil test.