drm/i915/uncore: Drop gen11 mmio read handlers

Consolidate down to just a single 'fwtable' implementation.  For reads
we don't need to worry about shadow tables.

While consolidating the functions, gen11/gen12 pick up a
NEEDS_FORCE_WAKE() check that they didn't have before, allowing them to
bypass a lot of forcewake/shadow checking for non-GT registers (e.g.,
display).

v2:
 - Restore NEEDS_FORCE_WAKE() check.  (Chris, Tvrtko)

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210910201030.3436066-6-matthew.d.roper@intel.com