drm/i915/display: Extract display workarounds from clock gating init

Several of the register updates that are currently done in the clock
gating init functions are actually display workarounds that should move
into the display-specific part of the code. Furthermore, some of the
registers being programmed don't even have anything to do with clock
gating at all.

Extract the display workarounds for gen11 and later platforms to a
dedicated display/intel_display_wa.c file to keep these separate from
the SOC / sgunit clock gating that we need on some platforms. The gen11
cutoff here is selected somewhat arbitrarily; this is the point where
workarounds were first assigned dedicated lineage numbers that can be
easily looked up and confirmed in the modern workaround database. It
also avoids any confusion on older platforms where the exact boundaries
between display/GT/other IP blocks wasn't as well-defined as it is
today.

Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230907001009.3732474-2-matthew.d.roper@intel.com