i965: Implement textureSize (TXS) on Gen4.

i965: Implement textureSize (TXS) on Gen4.

Also, remove the BRW_SAMPLER_MESSAGE_SIMD8_RESINFO #define because
there totally isn't a SIMD8 variant.

Unfortunately, resinfo returns FLOAT32 on Broadwater/Crestline, unlike
G45 which returns a proper UINT32.  This turns out to be simple,
however: when we emit MOVs to select the desired half of the SIMD16
result, we can simply override the register type to be float so it's
converted to an integer.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>