drm/omap: fix TILER on OMAP5

On OMAP5 it is not possible to use TILER buffer with CPU when caching or
write-combining is used. Doing so leads to errors from the memory
manager.

However, on OMAP4, write-combining works fine.

This patch adds platform specific data for the TILER, and a function
tiler_get_cpu_cache_flags() which can be used to get the caching mode to
be used.

Note that without write-combining the use of the TILER buffer with CPU
is unusably slow. It's still good to have it operational for testing
purposes.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
diff --git a/drivers/gpu/drm/omapdrm/omap_gem.c b/drivers/gpu/drm/omapdrm/omap_gem.c
index 9b250c9..d37ee75 100644
--- a/drivers/gpu/drm/omapdrm/omap_gem.c
+++ b/drivers/gpu/drm/omapdrm/omap_gem.c
@@ -1359,8 +1359,8 @@
 		/* currently don't allow cached buffers.. there is some caching
 		 * stuff that needs to be handled better
 		 */
-		flags &= ~(OMAP_BO_CACHED|OMAP_BO_UNCACHED);
-		flags |= OMAP_BO_WC;
+		flags &= ~(OMAP_BO_CACHED|OMAP_BO_WC|OMAP_BO_UNCACHED);
+		flags |= tiler_get_cpu_cache_flags();
 
 		/* align dimensions to slot boundaries... */
 		tiler_align(gem2fmt(flags),