ARM: dts: armada-38x: Fix compatible string for gpios
Armada 38x supports per CPU interrupts for gpios, like Armada XP. Pre-XP
variants like Armada 370 do not support per CPU interrupts for gpios.
So change compatible string for Armada 38x from "marvell,armada-370-gpio"
which indicates pre-XP variant to "marvell,armadaxp-gpio" which indicates
XP variant or new.
Driver gpio-mvebu.c which handles both pre-XP and XP variants already
provides support for per CPU interrupts on XP and newer variants.