media: i2c: ds90ub960: Reduce sleep in ub960_rxport_wait_locks()

We currently sleep for 50 ms at the end of each iteration in
ub960_rxport_wait_locks(). This feels a bit excessive, especially as we
always do at least two loops, so there's always at least one sleep, even
if we already have a stable lock.

Change the sleep to 10 ms.

Reviewed-by: Jai Luthra <jai.luthra@ideasonboard.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>