mhi: cntrl: qcom: transition to power off as soon as possible

As soon as MHI host receive power off request, transition host
state to power off to avoid unnecessary PCIe link resume.

CRs-Fixed: 2418550
Change-Id: If0f9301e59bd66928de6d65122f174e1031f967a
Signed-off-by: Sujeev Dias <sdias@codeaurora.org>