media: imx: vdic: Restore default case to prepare_vdi_in_buffers()

Restore a default case to prepare_vdi_in_buffers() to fix the following
smatch errors:

drivers/staging/media/imx/imx-media-vdic.c:236 prepare_vdi_in_buffers() error: uninitialized symbol 'prev_phys'.
drivers/staging/media/imx/imx-media-vdic.c:237 prepare_vdi_in_buffers() error: uninitialized symbol 'curr_phys'.
drivers/staging/media/imx/imx-media-vdic.c:238 prepare_vdi_in_buffers() error: uninitialized symbol 'next_phys'.

Fixes: 6e537b58 ("media: imx: vdic: rely on VDIC for correct field order")

Reported-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Steve Longerbeam <slongerbeam@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>