mhi: core: unconditionally trigger resume to assert device wake

In order to ensure that a DRV resume follows immediately after
a client calls device wake assert or deassert, MHI core driver
must unconditionally increment the PM runtime usage count and
post a wake source before waiting for the state change.

Change-Id: I50228742c090a5df6fcb06f89f53723179bcd76d
Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>