usb: dwc3-msm: Do dwc3_msm_gadget_vbus_draw() in sleepable context

The gadget mode notification to draw a specific current may
occur in context with interrupts disabled, however the charger
driver's implementation of power_supply_set_property() for
POWER_SUPPLY_CURRENT_MAX currently uses a mutex. Since
sleeping is disallowed in this case, instead schedule a
work function to do the call.

Change-Id: I810ad8c102124ce22de72d83b6df58c8fc991251
Signed-off-by: Jack Pham <jackp@codeaurora.org>