[media] m88rs2000 - only flip bit 2 on reg 0x70 on 16th try

Continuous flip of bit2 reg 0x70 can cause device to become unresponsive.

Also correct reg read mistake.

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