eeprom: at24: Use dev_err_probe for nvmem register failure

When using nvmem layouts it is possible devm_nvmem_register returns
-EPROBE_DEFER, resulting in an 'empty' in
/sys/kernel/debug/devices_deferred. Use dev_err_probe for providing
additional information.

Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>