i965/compute: Fix undefined code with right_mask for SIMD32
i965/compute: Fix undefined code with right_mask for SIMD32

Although we don't support SIMD32, krh pointed out that the left shift
by 32 is undefined by C/C++ for 32-bit integers.

Suggested-by: Kristian Høgsberg <ca9b5b1e27d4fa7f4ba6848bdd08ca52cfd6330c@bitplanet.net>
Signed-off-by: Jordan Justen <a79006884ba9cf5f4f7fcbb92a15b208780d8c97@intel.com>
Reviewed-by: Kenneth Graunke <bd2562f754ec92342f93f61c25d731e290a2ffa8@whitecape.org>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler