[media] uvcvideo: Add support for NOMMU arch

Add support to uvc driver for NOMMU arch including add function
uvc_queue_get_unmapped_area() and make some changes in uvc_queue_mmap().
So that uvc camera can be used on nommu arch like blackfin.

Signed-off-by: Bob Liu <lliubbo@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>