[media] [trivial] mantis: Fix typo in mantis_hif.c

Correct typo "Adater" to "Adapter" in
drivers/media/dvb/mantis/mantis_hif.c

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>