drm/udl: Fix unaligned memory access in udl_render_hline

On SPARC, the udl driver filled my kernel log with these messages:

[186668.910612] Kernel unaligned access at TPC[76609c] udl_render_hline+0x13c/0x3a0

Use put_unaligned_be16 to avoid them. On x86 this results in the same
code, but on SPARC the compiler emits two single-byte stores.

Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Acked-by: David Airlie <airlied@linux.ie>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20170407200229.20642-1-j.neuschaefer@gmx.net

drivers/gpu/drm/udl/udl_transfer.c

@@ -14,6 +14,7 @@
 #include <linux/slab.h>
 #include <linux/fb.h>
 #include <linux/prefetch.h>
+#include <asm/unaligned.h>
 
 #include <drm/drmP.h>
 #include "udl_drv.h"
@@ -163,7 +164,7 @@ static void udl_compress_hline16(
 			const u8 *const start = pixel;
 			const uint16_t repeating_pixel_val16 = pixel_val16;
 
-			*(uint16_t *)cmd = cpu_to_be16(pixel_val16);
+			put_unaligned_be16(pixel_val16, cmd);
 
 			cmd += 2;
 			pixel += bpp;