r600/shader: add utility functions to do single slot arithmatic
r600/shader: add utility functions to do single slot arithmatic

These utilities are to be used to do things like integer adds and
multiplies to be used in calculating the LDS offsets etc.

It handles CAYMAN MULLO differences as well.

Signed-off-by: Dave Airlie <f2295d84e358395675bc8031be58672073ae065e@redhat.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler