V4L/DVB (13607): vpif: move vpif_remove to .devexit

The function vpif_remove is used only wrapped by __devexit_p so define
it using __devexit.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>