slim: msm: Revert runtime-PM for Slimbus MSM controller

Using runtime-PM for slimbus MSM controller may cause some race
conditions (e.g. suspend callback is not guaranteed to be complete
when client calls pm_runtime_get_sync). Rely on system-wide suspend
resume callbacks till the race conditions are sorted out.

Change-Id: Ie41aa9fd64c437fc7e2f5699439ca78dedb74cde
Signed-off-by: Sagar Dharia <sdharia@codeaurora.org>