drm/i915: Enable WaProgramMgsrForCorrectSliceSpecificMmioReads for Gen9

This implements WaProgramMgsrForCorrectSliceSpecificMmioReads which
was omitted by mistake from Gen9 documentation, while it is actually
applicable to fused off parts.

Workaround consists of making sure MCR packet control register is
programmed to point to enabled slice/subslice pair before doing any
MMIO reads from the affected registers.

Failure do to this can result in complete system hangs when running
certain workloads. Two known cases which can cause system hangs are:

1. "test_basic progvar_prog_scope_uninit" test which is part of
    Khronos OpenCL conformance suite
    (https://github.com/KhronosGroup/OpenCL-CTS) with the Intel
    OpenCL driver (https://github.com/intel/compute-runtime).

2. VP8 media hardware encoding using the full-feature build of the
    Intel media-driver (https://github.com/intel/media-driver

) and
    ffmpeg.

For the former case patch was verified to fix the hard system hang
when executing the OCL test on Intel Pentium CPU 6405U which contains
fused off GT1 graphics.

Reference: HSD#1508045018,1405586840, BSID#0575

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: William Tseng <william.tseng@intel.com>
Cc: Shawn C Lee <shawn.c.lee@intel.com>
Cc: Pawel Wilma <pawel.wilma@intel.com>
Signed-off-by: Cooper Chiou <cooper.chiou@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Acked-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211025042623.3876-1-cooper.chiou@intel.com