nir: add missing GLSL_TYPE_DOUBLE case in type_size()
nir: add missing GLSL_TYPE_DOUBLE case in type_size()

To silence compiler warning about unhandled switch case.
v2: move GLSL_TYPE_DOUBLE to the "not reached" section, per Ilia.

Reviewed-by: Ilia Mirkin <bcbbb7aa705ec3a5fc5824c01a845186c3d62fca@alum.mit.edu>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler