V4L/DVB (11205): pvrusb2: Remove ancient IVTV specific ioctl functions

Remove ancient IVTV_IOC_G_CODEC and IVTV_IOC_S_CODEC ioctl functions
from the pvrusb2 driver.  These are very very old, were non-standard,
and were only present to keep MythTV happy (their implementation did
nothing except to report success).  That was long ago; no recent
versions of MythTV should require this anymore.

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