[media] omap_vout: fix compile warnings

When compiling under COMPILE_TEST on a x86_64 the following warnings
appear:

drivers/media/platform/omap/omap_vout.c: In function 'omap_vout_uservirt_to_phys':
drivers/media/platform/omap/omap_vout.c:209:23: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
   return virt_to_phys((void *) virtp);
                       ^
drivers/media/platform/omap/omap_vout.c: In function 'omapvid_setup_overlay':
drivers/media/platform/omap/omap_vout.c:420:2: warning: format '%x' expects argument of type 'unsigned int', but argument 5 has type 'dma_addr_t' [-Wformat=]
  v4l2_dbg(1, debug, &vout->vid_dev->v4l2_dev,
  ^
drivers/media/platform/omap/omap_vout.c: In function 'omap_vout_buffer_prepare':
drivers/media/platform/omap/omap_vout.c:794:34: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
   vout->queued_buf_addr[vb->i] = (u8 *)
                                  ^
In file included from arch/x86/include/asm/dma-mapping.h:44:0,
                 from include/linux/dma-mapping.h:82,
                 from drivers/media/platform/omap/omap_vout.c:40:
drivers/media/platform/omap/omap_vout.c:803:58: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
   dma_addr = dma_map_single(vout->vid_dev->v4l2_dev.dev, (void *) addr,
                                                          ^
include/asm-generic/dma-mapping-common.h:174:60: note: in definition of macro 'dma_map_single'
 #define dma_map_single(d, a, s, r) dma_map_single_attrs(d, a, s, r, NULL)
                                                            ^

These are fixed by this patch.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>