msm: ipa3: wait for uC load before USB disconnect

In case RG10 workaround is in use, USB disconnect sequence
needs to be delayed until uC image is loaded in order to
allow to suspend and unsuspend pipes successfully.

Change-Id: I0ba41c9564c12b0b2c419222b54fa0e05be93b75
CRs-Fixed: 1083675
Acked-by: Ady Abraham <adya@qti.qualcomm.com>
Signed-off-by: Skylar Chang <chiaweic@codeaurora.org>