drm: Fix broken use of _PAGE_NO_CACHE on powerpc

That constant isn't meant to be used outside of arch mm code

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1467018023.20278.65.camel@kernel.crashing.org
diff --git a/drivers/gpu/drm/drm_memory.c b/drivers/gpu/drm/drm_memory.c
index 87a8cb7..fc0ebd2 100644
--- a/drivers/gpu/drm/drm_memory.c
+++ b/drivers/gpu/drm/drm_memory.c
@@ -44,7 +44,7 @@
 # include <asm/agp.h>
 #else
 # ifdef __powerpc__
-#  define PAGE_AGP	__pgprot(_PAGE_KERNEL | _PAGE_NO_CACHE)
+#  define PAGE_AGP	pgprot_noncached_wc(PAGE_KERNEL)
 # else
 #  define PAGE_AGP	PAGE_KERNEL
 # endif