soc: swr-mstr: Resolve swr overflow, underflow errors for wsa

SWR overflow, underflow interrupts are seen sometimes on bootup.
Check whether devnum is 0 during fifo read and write. Also assign
read and write fifo depth before master init to resolve errors.

Change-Id: Id7b687985e320396d2f9dab69db56cc7f5426b04
Signed-off-by: Vatsal Bucha <vbucha@codeaurora.org>