mesa: refactor GetFragDataIndex
mesa: refactor GetFragDataIndex

Use _mesa_program_resource_location_index to fetch index.

Signed-off-by: Tapani Pälli <cdcb67a5e49297de94340ca09f25994bd5e7f762@intel.com>
Reviewed-by: Ilia Mirkin <bcbbb7aa705ec3a5fc5824c01a845186c3d62fca@alum.mit.edu>
Reviewed-by: Martin Peres <f078f77bcd6141e84e4eefdc58402db4e0e36622@linux.intel.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler