mhi: core: force wake when exiting MHI suspend (M3) state

It's possible for MHI host to exit M3 and enter low power mode
by the time resume thread wakes up from M0 signal. To prevent
transitioning into low power mode, keep wake asserted until
host wakes up from M0 signal transition.

CRs-Fixed: 2360155
Change-Id: If94b3a23eeda711bd70932279e60bcb80c465b31
Signed-off-by: Sujeev Dias <sdias@codeaurora.org>