msm: vidc: retain clock rate across power suspend/resume

Power collapse should be transparent to vidc layer, so
clock rate should be retained across suspend resume.

Add change to save clock rate during suspend, and restore
clock rate during resume.

Change-Id: I7e01ddcfc5b2f7d02f76512e1cbaf1a75bacdb03
Signed-off-by: Surajit Podder <spodder@codeaurora.org>