V4L/DVB (5583): VIDEO4LINUX-2: Replace MINOR() with a call to iminor().

Replace the call to MINOR() with a call to the inline iminor()
routine.

Signed-off-by: Robert P. J. Day <rpjday@mindspring.com>
Acked-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>