soc: qcom: smd: Fix init irq race condition

There is a small window where SMD could recieve an IRQ, but is not fully
ready to process it yet.  This window could result in an access to invalid
data.

Avoid accesses to invalid data by not processing interrupts before the
driver is fully ready to do so.  Any skipped activity will be processed at
the end of init.

Change-Id: If61a8d25502c69f0925a99ba5fc14c26c3542811
Signed-off-by: Jeffrey Hugo <jhugo@codeaurora.org>