power: reset: odroid-go-ultra: fix I2C dependency

Since this driver can only be built-in, it fails to link when
the I2C layer is in a loadable module:

x86_64-linux-ld: drivers/power/reset/odroid-go-ultra-poweroff.o: in function `odroid_go_ultra_poweroff_get_pmic_device':
odroid-go-ultra-poweroff.c:(.text+0x30): undefined reference to `i2c_find_device_by_fwnode'

Tighten the dependency to only allow enabling
POWER_RESET_ODROID_GO_ULTRA_POWEROFF is I2C is built-in as well.

Fixes: cec3b46b ("power: reset: add Odroid Go Ultra poweroff driver")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>