i965/icl: Disable prefetching of sampler state entries

i965/icl: Disable prefetching of sampler state entries

In the same spirit as commit a5889d70f2074201ceaeac4f96a9a0c0b1f68a31
"i965/icl: Disable binding table prefetching". Fixes some 110+
intermittent piglit failures with tex-miplevel-selection variants.

WA_1606682166:
Incorrect TDL's SSP address shift in SARB for 16:6 & 18:8 modes.
Disable the Sampler state prefetch functionality in the SARB by
programming 0xB000[30] to '1'. This is to be done at boot time and
the feature must remain disabled permanently.

Anuj: Set SamplerCount = 0 for vs, gs, hs, ds and wm units as well.

Signed-off-by: Topi Pohjolainen <topi.pohjolainen@intel.com>
Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
Cc: Mark Janes <mark.a.janes@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>