Revert "drm/i915/dg2: Add preemption changes for Wa_14015141709"

Revert "drm/i915/dg2: Add preemption changes for Wa_14015141709"

This reverts commit ca6920811aa5428270dd78af0a7a36b10119065a.

The intent of Wa_14015141709 was to inform us that userspace can no
longer control object-level preemption as it has on past platforms
(i.e., by twiddling register bit CS_CHICKEN1[0]).  The description of
the workaround in the spec wasn't terribly well-written, and when we
requested clarification from the hardware teams we were told that on the
kernel side we should also probably stop setting
FF_SLICE_CS_CHICKEN1[14], which is the register bit that directs the
hardware to honor the settings in per-context register CS_CHICKEN1.  It
turns out that this guidance about FF_SLICE_CS_CHICKEN1[14] was a
mistake; even though CS_CHICKEN1[0] is non-operational and useless to
userspace, there are other bits in the register that do still work and
might need to be adjusted by userspace in the future (e.g., to implement
other workarounds that show up).  If we don't set
FF_SLICE_CS_CHICKEN1[14] in i915, then those future workarounds would
not take effect.

This miscommunication came to light because another workaround
(Wa_16013994831) has now shown up that requires userspace to adjust the
value of CS_CHICKEN[10] in certain circumstances.  To ensure userspace's
updates to this chicken bit are handled properly by the hardware, we
need to make sure that FF_SLICE_CS_CHICKEN1[14] is once again set by the
kernel.

Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Matt Atwood <matthew.s.atwood@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220826210233.406482-1-matthew.d.roper@intel.com