mesa/main/ff_frag: Reduce the size of nr_enabled_units.
mesa/main/ff_frag: Reduce the size of nr_enabled_units.

Since it holds values from 0 to 8, 4 bits will suffice.

Signed-off-by: Gustaw Smolarczyk <c5b012c207a4d1772b2d0494e7632306fbe4aa93@gmail.com>
Reviewed-by: Eric Anholt <96f164ad4d9b2b0dacf8ebee2bb1eeb3aa69adf1@anholt.net>
Signed-off-by: Marek Olšák <8c7344a1abdb103e79ecfd488098373070c3c70e@amd.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler