msm: bam_dmux: move sps_disconnect calls to the reconnect case

The A2 BAM hardware may be powered off when disconnect_to_bam() is called.
If so, sps_disconnect() will cause L2 errors a possibly a watchdog crash.
Move the sps_disconnect() calls to the reconnect case where A2 BAM has
powered back up and it is safe to call sps_disconnect()

CRs-Fixed: 402645
Change-Id: I4a365a3a4b91255429cbc326f31ab29aacc273b6
Signed-off-by: Jeffrey Hugo <jhugo@codeaurora.org>