media: ov2740: Drop redundant assignments of ret = 0

In some cases it might hide real bugs, in most cases here it's just
redundant as it's being reassigned immediately after initial assignment.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>