cnss2: Do not suspend MHI if PCIe is not going to be suspended

If PCIe doesn't suspend while MHI does, MHI driver may miss some
firmware notifications. Hence add the support that if PCIe is not
going to be suspended, do not suspend MHI as well.

Change-Id: Ibc6907a002c6299e1949ad13e322b1febee8ac09
Signed-off-by: Yue Ma <yuem@codeaurora.org>