drm/i915/gtt: No need to zero the table for page dirs

We set them to scratch right after allocation so prevent
useless zeroing before.

v2: atomic_t
v3: allow pdp alloc fail

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190614164350.30415-1-mika.kuoppala@linux.intel.com

drivers/gpu/drm/i915/i915_gem_gtt.c

@@ -688,7 +688,7 @@ static struct i915_page_directory *alloc_pd(struct i915_address_space *vm)
 {
 	struct i915_page_directory *pd;
 
-	pd = kzalloc(sizeof(*pd), I915_GFP_ALLOW_FAIL);
+	pd = kmalloc(sizeof(*pd), I915_GFP_ALLOW_FAIL);
 	if (unlikely(!pd))
 		return ERR_PTR(-ENOMEM);
 
@@ -748,7 +748,7 @@ alloc_pdp(struct i915_address_space *vm)
 
 	GEM_BUG_ON(!i915_vm_is_4lvl(vm));
 
-	pdp = kzalloc(sizeof(*pdp), GFP_KERNEL);
+	pdp = kmalloc(sizeof(*pdp), I915_GFP_ALLOW_FAIL);
 	if (!pdp)
 		return ERR_PTR(-ENOMEM);