drm/i915/: Re-work clflush_write32

Use drm_clflush_virt_range instead of clflushopt and remove the memory
barrier, since drm_clflush_virt_range takes care of that.

v2(Michael Cheng): Use sizeof(*addr) instead of sizeof(addr) to get the
		   actual size of the page. Thanks to Matt Roper for
		   pointing this out.
Signed-off-by: Michael Cheng <michael.cheng@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220321223819.72833-5-michael.cheng@intel.com

drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c

@@ -1322,10 +1322,8 @@ static void *reloc_vaddr(struct i915_vma *vma,
 static void clflush_write32(u32 *addr, u32 value, unsigned int flushes)
 {
 	if (unlikely(flushes & (CLFLUSH_BEFORE | CLFLUSH_AFTER))) {
-		if (flushes & CLFLUSH_BEFORE) {
-			clflushopt(addr);
-			mb();
-		}
+		if (flushes & CLFLUSH_BEFORE)
+			drm_clflush_virt_range(addr, sizeof(*addr));
 
 		*addr = value;
 
@@ -1337,7 +1335,7 @@ static void clflush_write32(u32 *addr, u32 value, unsigned int flushes)
 		 * to ensure ordering of clflush wrt to the system.
 		 */
 		if (flushes & CLFLUSH_AFTER)
-			clflushopt(addr);
+			drm_clflush_virt_range(addr, sizeof(*addr));
 	} else
 		*addr = value;
 }