gallium: rename TGSI shader-caps
These are no longer TGSI specific, so let's rename them to reflect reality.
The only TGSI-specific ones left are now these:
PIPE_SHADER_CAP_TGSI_SQRT_SUPPORTED
PIPE_SHADER_CAP_TGSI_FMA_SUPPORTED
PIPE_SHADER_CAP_TGSI_ANY_INOUT_DECL_RANGE
PIPE_SHADER_CAP_TGSI_SKIP_MERGE_REGISTERS
These are all only used by TGSI codepaths.