V4L/DVB (5041): Pvrusb2: Use separate enumeration for get/store of minor number

Use separate enum for get/store of minor number; we want pvr2_config
to go away eventually and since it really means something different,
don't use it here

Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>