i965/skl: Break down SIMD16 3-source instructions when required.
i965/skl: Break down SIMD16 3-source instructions when required.

Several steppings of Skylake fail when using SIMD16 with 3-source
instructions (such as MAD).

This implements WaDisableSIMD16On3SrcInstr and fixes ~190 Piglit
tests.

Based on a patch by Neil Roberts.

Signed-off-by: Kenneth Graunke <bd2562f754ec92342f93f61c25d731e290a2ffa8@whitecape.org>
Reviewed-by: Neil Roberts <822ec91a7ef82248fd36162ca8ac3283eba70848@linux.intel.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler