pci: msm: Fix spinlock lockup during notify_client

Currently interrupts are not being disabled locally
when an event callback is being used.
This can lead to a scenario where we try to acquire
the same lock as part of global irq handler when
a client callback was in progress.

Fix this by disabling the interruts locally by using
a irqsave version of spinlock when an event callback
is being used.

Change-Id: I8a2eff826e24fb32c60bd5769390faa960669eb7
Signed-off-by: Sriharsha Allenki <sallenki@codeaurora.org>