msm: bam_dmux: reset wakelock flag during subsystem restart

Reset the flag that prevents grabbing the wakelock the first time
modem boots up when a subsystem restart event occurs.  This keeps the
wakelock reference count consistant after a restart event so that
bam_dmux does not end up holding the wakelock for longer than needed.

CRs-Fixed: 333552
Change-Id: Iaa149f35059277289a00bb77608be2b2f7f8edbe
Signed-off-by: Jeffrey Hugo <jhugo@codeaurora.org>