[media] iguanair: simplify calculation of carrier delay cycles

Simplify the logic that	calculates the carrier,	and removes a warning
on avr32 arch:
        drivers/media/rc/iguanair.c: In function 'iguanair_set_tx_carrier':
        drivers/media/rc/iguanair.c:304: warning: 'sevens' may be used uninitialized in this function

Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
Reviewed-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>