usb: dwc3-msm: Remove call to set POWER_SUPPLY_PROP_ONLINE

The charger drivers now handle setting of this property without
input from USB gadget other than the negotiated current draw
amount (set via POWER_SUPPLY_PROP_CURRENT_MAX). Remove setting
of POWER_SUPPLY_PROP_ONLINE which helps simplify the
dwc3_msm_gadget_vbus_draw() function a bit.

Change-Id: I2c5ec90cc8c45019ad75056b6feb7e6319f85514
Signed-off-by: Jack Pham <jackp@codeaurora.org>