drm/i915/gtt: remove px_page

Entries will either be pointing to scratch or real PD, making the
px_page(pd) check pointless. Also since there are no other users of
px_page, just remove it.

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michel Thierry <michel.thierry@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180730120544.20784-1-matthew.auld@intel.com

drivers/gpu/drm/i915/i915_gem_gtt.c

@@ -1251,9 +1251,6 @@ static void gen8_free_page_tables(struct i915_address_space *vm,
 {
 	int i;
 
-	if (!px_page(pd))
-		return;
-
 	for (i = 0; i < I915_PDES; i++) {
 		if (pd->page_table[i] != vm->scratch_pt)
 			free_pt(vm, pd->page_table[i]);

drivers/gpu/drm/i915/i915_gem_gtt.h

@@ -229,7 +229,6 @@ struct i915_page_dma {
 };
 
 #define px_base(px) (&(px)->base)
-#define px_page(px) (px_base(px)->page)
 #define px_dma(px) (px_base(px)->daddr)
 
 struct i915_page_table {