mvebu/omnia: fix the device tree

mvebu/omnia: fix the device tree

Backport [1] and fix [2] hardware buffer management. Also fix the IRQ storm
caused by a misconfiguration of the PCA9538 interrupt pin [3].

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/arch/arm/boot/dts/armada-385-turris-omnia.dts?id=018b88eee1a2efda26ed2f09aab33ccdc40ef18f
[2] https://lore.kernel.org/linux-arm-kernel/20210217153038.1068170[email protected]/
[3] https://lore.kernel.org/linux-arm-kernel/20210220231144[email protected]/

Signed-off-by: Rui Salvaterra <[email protected]>
(cherry picked from commit 6fe6b631ef91a8a44d7324329ad6aaec6f08ada6)