V4L/DVB (4395): Restore compat_ioctl in pwc driver

The compat_ioctl support of the pwc driver was dropped during the last update of the driver.
I suppose it was by mistake. If yes here is the patch to restore the support.

Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@looxix.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>