glsl: add fallthrough comment on switch
glsl: add fallthrough comment on switch

Signed-off-by: Tapani Pälli <cdcb67a5e49297de94340ca09f25994bd5e7f762@intel.com>
Reviewed-By: Martin Peres <f078f77bcd6141e84e4eefdc58402db4e0e36622@linux.intel.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler