wcnss: Convert FIQ register address from virtual to physical

bit 16 of the APCS_IPC_INTERRUPT is used to trigger an FIQ to Pronto
when there is a WDI timeout. Convert APCS_IPC_INTERRUPT register
address to physical address. This change also adds a DT entry for FIQ
register.

Change-Id: I10638248a7fca2eb68f84e1f0c9c4ccc119f828b
Signed-off-by: Sameer Thalappil <sameert@codeaurora.org>