drm/i915/gt: Prevent error pointer dereference

Move the check for "if (IS_ERR(obj))" in front of the call to
i915_gem_object_set_cache_coherency() which dereferences "obj".
Otherwise it will lead to a crash.

Fixes: 43aa755e ("drm/i915/mtl: Update cache coherency setting for context structure")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/455b2279-2e08-4d00-9784-be56d8ee42e3@moroto.mountain
(cherry picked from commit c92ec508)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

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

@@ -1094,6 +1094,9 @@ __lrc_alloc_state(struct intel_context *ce, struct intel_engine_cs *engine)
 					  I915_BO_ALLOC_PM_VOLATILE);
 	if (IS_ERR(obj)) {
 		obj = i915_gem_object_create_shmem(engine->i915, context_size);
+		if (IS_ERR(obj))
+			return ERR_CAST(obj);
+
 		/*
 		 * Wa_22016122933: For Media version 13.0, all Media GT shared
 		 * memory needs to be mapped as WC on CPU side and UC (PAT
@@ -1102,8 +1105,6 @@ __lrc_alloc_state(struct intel_context *ce, struct intel_engine_cs *engine)
 		if (intel_gt_needs_wa_22016122933(engine->gt))
 			i915_gem_object_set_cache_coherency(obj, I915_CACHE_NONE);
 	}
-	if (IS_ERR(obj))
-		return ERR_CAST(obj);
 
 	vma = i915_vma_instance(obj, &engine->gt->ggtt->vm, NULL);
 	if (IS_ERR(vma)) {