Revert "ARM: dts: armada-39x: Fix compatible string for gpios"

This reverts commit d10886a4.

If compatible = "marvell,armadaxp-gpio", the reg property requires a
second (address, size) pair, which points to the per-CPU interrupt
registers <0x18800 0x30> / <0x18840 0x30>.

Furthermore:
Commit 5f79c651 explains very well, why the gpio-mvebu driver does not
work reliably with per-CPU interrupts.
Commit 988c8c0c deprecates compatible = marvell,armadaxp-gpio for this
reason.

Signed-off-by: Klaus Kudielka <klaus.kudielka@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>