ramips: zbt-wg2626: Add the reset gpio for PCIe port 1

ramips: zbt-wg2626: Add the reset gpio for PCIe port 1

The 2.4GHz interface doesn't come up properly with the log showing:

    mt7621-pci 1e140000.pcie: pcie1 no card, disable it (RST & CLK)

As seen on other MT7621 boards this is caused by a missing reset GPIO.
The MT7621 dtsi set GPIO 19 as PCIe reset GPIO, which on this board
reset the 5GHz interface on port 0. Add GPIO 8 to the PCIe reset GPIO
list to also reset the 2.4GHz interface on port 1.

Signed-off-by: Alban Bedel <albeu@free.fr>
(cherry picked from commit f953a1a4bfba2fa70c12bb80938aa66481a673b6)