usb: dwc2: fix call to vbus supply exit routine, call it unlocked

dwc2_vbus_supply_exit() may call regulator_disable(). It shouldn't be
called with interrupts disabled as it might sleep.
This is seen with DEBUG_ATOMIC_SLEEP=y.

Fixes: 531ef5eb ("usb: dwc2: add support for host mode external
vbus supply")

Tested-by: Artur Petrosyan <arturp@synopsys.com>
Acked-by: Minas Harutyunyan <hminas@synopsys.com>
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Signed-off-by: Amelie Delaunay <amelie.delaunay@st.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>