i965/ivb: Flag RG32F quirk for texture gather regardless of swizzles

i965/ivb: Flag RG32F quirk for texture gather regardless of swizzles

As of ARB_gpu_shader5, textureGather doesn't always read the
post-swizzle RED channel -- so we can't just look at the red swizzle
state.

Theoretically we could only flag the quirk if *some* green swizzle is in
use, but that's probably more trouble than it's worth.

Signed-off-by: Chris Forbes <chrisf@ijw.co.nz>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>