drm/i915: use uncached writes in pwrite

It's around 20% faster.
Tested-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-Off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gem.c

@@ -642,9 +642,9 @@ i915_gem_shmem_pwrite(struct drm_device *dev,
 			if (partial_cacheline_write)
 				drm_clflush_virt_range(vaddr + shmem_page_offset,
 						       page_length);
-			ret = __copy_from_user_inatomic(vaddr + shmem_page_offset,
-							user_data,
-							page_length);
+			ret = __copy_from_user_inatomic_nocache(vaddr + shmem_page_offset,
+								user_data,
+								page_length);
 			if (needs_clflush_after)
 				drm_clflush_virt_range(vaddr + shmem_page_offset,
 						       page_length);