Our sanitychecks indicate that while this register is context
saved/restore, the HW does not preserve this bit within the register --
it likely doesn't exist, or one of those mythical bits that the
architects insist does something despite all appearances to the
contrary.

For reference, SAMPLER_MODE is already in i915_reg.h as
GEN10_SAMPLER_MODE and is being setup in icl_ctx_workarounds_init() as
opposed to the chosen location here of rcs_engine_wa_init).

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111754
Fixes: 7f0cc34b ("drm/i915/tgl: Implement Wa_1406941453")
Testcase: igt/i915_selftest/live_workarounds
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Stuart Summers <stuart.summers@intel.com>
Cc: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Acked-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190920081254.18389-1-chris@chris-wilson.co.uk