mailbox: msm_qmp: Differentiate early boot procs

The shared memory used in QMP maybe owned by the remote proc and not be
clocked while the processor is in reset. The fake rx interrupt should
only be done on processors that are booted before the APPS proc.

Change-Id: I090bcbaee4333020b911c8643a95d8b40c9eb100
Signed-off-by: Chris Lew <clew@codeaurora.org>