leds: tca6507: fix potential zero passed to ERR_PTR

Fix potential ERR_PTR(0).

Signed-off-by: Marek Behún <kabel@kernel.org>
Fixes: d78b10f5713d9 ("leds: tca6507: use fwnode API instead of OF")
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Pavel Machek <pavel@ucw.cz>