leds: simatic-ipc-leds-gpio: Make simatic_ipc_led_gpio_table static

simatic_ipc_led_gpio_table is only used inside simatic-ipc-leds-gpio.c,
make it static.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20220910085836.84962-1-hdegoede@redhat.com