msm: bam_dmux: Remove SSR after shutdown_completion timeout

The modem restart introduced by following commit
3d04101 msm: bam_dmux: delay shutdown until DL polling is complete
is seen to be called incorrectly even when modem is up normally.

Avoid condition by:
1) Removed SSR upon shutdown completetion timeout to make
   behaviour similar to previous releases
2) Increased the SHUTDOWN_TIMEOUT_MS from 500ms to 2s as per QC suggestion

Change-Id: Ic7b9f5661b8eed8b12455a4295ff1b738e6a76b7
Signed-off-by: A. Kaul <w42726@motorola.com>
Reviewed-on: http://gerrit.pcs.mot.com/624505
SLTApproved: Slta Waiver <sltawvr@motorola.com>
Tested-by: Jira Key <jirakey@motorola.com>
Reviewed-by: Jayachandran Chinnakkannu <jayc@motorola.com>
Reviewed-by: Christopher Fries <c.fries@motorola.com>
Submit-Approved: Maulik Desai <amd093@motorola.com>
(cherry picked from commit 55b2454d4b0b0c1e81b20fdca88d5dd02021fb2c)
Reviewed-on: http://gerrit.pcs.mot.com/625599
Reviewed-by: Upgrade Build <dbbuild@motorola.com>
SLTApproved: Upgrade Build <dbbuild@motorola.com>
Submit-Approved: Upgrade Build <dbbuild@motorola.com>
Tested-by: Upgrade Build <dbbuild@motorola.com>