mhi: core: make timesync register access strict

Ensure timesync register access is only attempted if both pm
states allow it to prevent unclocked access leading to NOC
errors when any of the pm states is a false-positive.

CRs-Fixed: 2465813
Change-Id: I46eb2179ce406bef833cbeb7f1728871b54c4eaf
Acked-by: Bhaumik Vasav Bhatt <bbhatt@qti.qualcomm.com>
Signed-off-by: Tony Truong <truong@codeaurora.org>