msm: ipa: fix usb pm initialization

Initialize PM related members in IPA_USB always,
even if PM is not used. This is to avoid any race
conditions between different init functions.

Change-Id: I537b00030ee52f387cf92a9ec7065aa82191a979
CRs-Fixed: 2259107
Acked-by: Ady Abraham <adya@qti.qualcomm.com>
Signed-off-by: Skylar Chang <chiaweic@codeaurora.org>