usb: gadget: f_gsi: Store the return value of ipa_suspend_work_handler()

The return value of ipa_suspend_work_handler() is not stored in
ipa_work_handler(), in case of suspend event is received in connected
state. Sometimes even when ipa_suspend_work_handler() returns non-zero
value, usb_gadget_autopm_put_async() gets called, which causes the
pm_usage count to go negative.
Store the return value of ipa_suspend_work_handler() and then do a
put_sync only when the return value is 0.

Change-Id: I39dc8ac5b456f1c0c62cc4764be1670748fc284d
CRs-fixed: 958227
Signed-off-by: Azhar Shaikh <azhars@codeaurora.org>