mvebu: disable MSI interrupts

MSI interrupts do not seem to be working on mvebu, and they break
ath10k. Since nothing else seems to be using them, especially not
mwlwifi, disable them until we can fix MSI interrupts.

Works around the following issue:
[    9.001457] ath10k_pci 0000:02:00.0: failed to receive control response completion, polling..
[   10.001453] ath10k_pci 0000:02:00.0: Service connect timeout
[   10.007126] ath10k_pci 0000:02:00.0: failed to connect htt (-110)
[   10.092224] ath10k_pci 0000:02:00.0: could not init core (-110)
[   10.098177] ath10k_pci 0000:02:00.0: could not probe fw (-110)

Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
Acked-by: Felix Fietkau <nbd@nbd.name>