msm: bam_dmux: release read lock in error scenarios

If an error is encountered while writing, bail after releasing all
resources. The read lock needs to be released so that the write lock can
be grabbed if no other clients are holding the read lock, otherwise a
phantom client will always be holding the read lock thus starving the
write lock client.

Change-Id: I167d09c1f8c7b00563e9b398cbede50f9378c971
Signed-off-by: Jeffrey Hugo <jhugo@codeaurora.org>