mhi: cntrl: add support for advanced power management featues

Add support to allow system suspend while PCIe link is in
active state, allow host to initiate automatic suspend whenever
PCIe link is in idle state by taking advantage of L1ss inactivity
timer, and add support for drv handoff if soc supports it.

CRs-Fixed: 2418347
Change-Id: I02b66d790e7b8b625d186431d89f4d6bda5268d4
Signed-off-by: Sujeev Dias <sdias@codeaurora.org>