drm/i915: Remove dead code from gen8_pte_encode

Commit 9275277 ("drm/i915: use pat_index instead of cache_level")
added a dedicated gen12_pte_encode but forgot to remove the Gen12 specific
bit from gen8_pte_encode.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Fixes: 9275277 ("drm/i915: use pat_index instead of cache_level")
Cc: Fei Yang <fei.yang@intel.com>
Cc: Andi Shyti <andi.shyti@linux.intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Fei Yang <fei.yang@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230707124644.3965281-1-tvrtko.ursulin@linux.intel.com
(cherry picked from commit 0850937)
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Author: tursulin

drivers/gpu/drm/i915/gt/gen8_ppgtt.c

@@ -37,9 +37,6 @@ static u64 gen8_pte_encode(dma_addr_t addr,
 	if (unlikely(flags & PTE_READ_ONLY))
 		pte &= ~GEN8_PAGE_RW;
 
-	if (flags & PTE_LM)
-		pte |= GEN12_PPGTT_PTE_LM;
-
 	/*
 	 * For pre-gen12 platforms pat_index is the same as enum
 	 * i915_cache_level, so the switch-case here is still valid.