intel/compiler: Cast reg types explicitly

Makes coverity happier.

CID: 1416799
Fixes: c1ac1a3d25 (i965: Add a brw_hw_type_to_reg_type() function)

Reviewed-by: Matt Turner <mattst88@gmail.com>
Signed-off-by: Topi Pohjolainen <topi.pohjolainen@intel.com>
1 file changed