V4L/DVB (6751): V4L: Memory leak! Fix count in videobuf-vmalloc mmap

This is pretty serious bug.  map->count is never initialized after the
call to kmalloc making the count start at some random trash value.  The
end result is leaking videobufs.

Also, fix up the debug statements to print unsigned values.

Pushed to http://ifup.org/hg/v4l-dvb too

Signed-off-by: Brandon Philips <bphilips@suse.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>