clk: qcom: clock-cpu-8939: Keep clocks prepared across suspend/resume

Keep clocks prepared across suspend/resume since
regulator requests may fail when clocks are unprepared
during suspend, since regulator devices may be suspended.

CRs-Fixed: 762377
Change-Id: Ica18a8bb535ea8af7684b0cc63ba3c38e6648085
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>