x86, gart: Set DISTLBWALKPRB bit always

The DISTLBWALKPRB bit must be set for the GART because the
gatt table is mapped UC. But the current code does not set
the bit at boot when the BIOS setup the aperture correctly.
Fix that by setting this bit when enabling the GART instead
of the other places.

Cc: <[e-mail]>
Cc: Borislav Petkov <[e-mail]>
Signed-off-by: Joerg Roedel <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: H. Peter Anvin <[e-mail]>

arch/x86/include/asm/gart.h

···
 	 * Don't enable translation but enable GART IO and CPU accesses.
 	 * Also, set DISTLBWALKPRB since GART tables memory is UC.
 	 */
-	ctl = DISTLBWALKPRB | order << 1;
+	ctl = order << 1;
 
 	pci_write_config_dword(dev, AMD64_GARTAPERTURECTL, ctl);
 }
···
 
 	/* Enable GART translation for this hammer. */
 	pci_read_config_dword(dev, AMD64_GARTAPERTURECTL, &ctl);
-	ctl |= GARTEN;
+	ctl |= GARTEN | DISTLBWALKPRB;
 	ctl &= ~(DISGARTCPU | DISGARTIO);
 	pci_write_config_dword(dev, AMD64_GARTAPERTURECTL, ctl);
 }

arch/x86/kernel/aperture_64.c

···
 		 * Don't enable translation yet but enable GART IO and CPU
 		 * accesses and set DISTLBWALKPRB since GART table memory is UC.
 		 */
-		u32 ctl = DISTLBWALKPRB | aper_order << 1;
+		u32 ctl = aper_order << 1;
 
 		bus = amd_nb_bus_dev_ranges[i].bus;
 		dev_base = amd_nb_bus_dev_ranges[i].dev_base;