nir-to-tgsi: fix swizzle for double immediate
Use ureg_DECL_immediate_uint64 to declare double immediate, otherwise the swizzle for a double might not be in the valid form, ie. must be either .xy or .zw
Use ureg_DECL_immediate_uint64 to declare double immediate, otherwise the swizzle for a double might not be in the valid form, ie. must be either .xy or .zw