pinctrl: realtek: rtd1625: fix base_bit for VE4 GPIO 13

Fix a typo in the base_bit of RTD1625_VE4_GPIO_13.
It was incorrectly set to 18, which overlaps with GPIO 16.

Signed-off-by: Yu-Chun Lin <eleanor.lin@realtek.com>
Signed-off-by: Linus Walleij <linusw@kernel.org>