[media] DocBook media typo

V4L2_CID_BASE_LASTP1 should be V4L2_CID_LASTP1. This has probably been wrong
since the earliest days of this documentation until I did a copy-and-paste
and found out that V4L2_CID_BASE_LASTP1 doesn't actually exist :-)

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>