[media] STV0288 increase delay between carrier search

The current delay of 30uS is too short to recover any carrier.

In the lmedm04 driver delays were added to overcome carrier lock
problems. The typical delay was 30mS (2 x 15ms register write
0x2c and read 0x24).

Other drivers that use STV0288 don't appear to have any delay are
likely to have also suffered this problem.

Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>