msm: bam_dmux: reset bam hardware when A2 goes into pc

Reset the bam hardware when A2 goes into power collapse so that the A2
can be reset after the disconnect ack is sent from bam_dmux to A2.  This
allows the A2 to remain in sync with the bam hardware which prevents
possible unrecoverable data stalls from occuring.

This change reverts commit b11a52c7748e3f5fba7850fb843cabd9ad4878e7 but
adds special handling for the subsystem restart case so that the issue
fixed by b11a52 is not reintroduced.

CRs-Fixed: 433400
Change-Id: Ie476e249b03bb6bd40abc8981472684664d34ae6
Signed-off-by: Jeffrey Hugo <jhugo@codeaurora.org>
Signed-off-by: Arun Kumar Neelakantam <aneela@codeaurora.org>