Clear the interrupt mask registers of ASB2364 peripherals before enabling
interrupts so that any peripherals that weren't dealt with by the bootloader
after a reboot (if there was one) won't cause an interrupt storm when
interrupts are first enabled before the drivers are initialised.

Also, attempt to reset the peripherals attached to the FPGA.
Signed-off-by: NDavid Howells <dhowells@redhat.com>