i965/vec4: Support arbitrarily large sampler state indices on Haswell+.

i965/vec4: Support arbitrarily large sampler state indices on Haswell+.

Like the scalar backend, we add an offset to the "Sampler State Pointer"
field to select a group of 16 samplers, then use the "Sampler Index"
field to select within that group.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Chris Forbes <chrisf@ijw.co.nz>