mhi: core: Check for pm error state before asserting dev wake

After calling remove call back in mhi_pm_disable_transition
there is possibility of MHI client calling mhi_device_get_sync
which increments dev wake. This results in to MHI ASSERT due
to non zero dev wake count. Fix this issue by checking pm error
state before incrementing dev wake count.

Change-Id: I817d571f210b77aef444a7ae1f9b2cc5af057ab2
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>