i965/tcs/scalar: only update imm_offset for second message in 64bit input loads
i965/tcs/scalar: only update imm_offset for second message in 64bit input loads

Our indirect URB read messages take both a direct and an indirect offset
so when we emit the second message for a 64-bit input load we can just
always incremement the immediate offset, even for the indirect case.

Reviewed-by: Timothy Arceri <5dd83789ef3714029244367ba1ca09f1d7627408@collabora.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler