usb: dwc2: drd: fix soft connect when gadget is unconfigured

When the gadget driver hasn't been (yet) configured, and the cable is
connected to a HOST, the SFTDISCON gets cleared unconditionally, so the
HOST tries to enumerate it.
At the host side, this can result in a stuck USB port or worse. When
getting lucky, some dmesg can be observed at the host side:
 new high-speed USB device number ...
 device descriptor read/64, error -110

Fix it in drd, by checking the enabled flag before calling
dwc2_hsotg_core_connect(). It will be called later, once configured,
by the normal flow:
- udc_bind_to_driver
 - usb_gadget_connect
   - dwc2_hsotg_pullup
     - dwc2_hsotg_core_connect

Fixes: 17f93402 ("usb: dwc2: override PHY input signals with usb role switch support")
Cc: stable@kernel.org
Reviewed-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
Acked-by: Minas Harutyunyan <Minas.Harutyunyan@synopsys.com>
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Link: https://lore.kernel.org/r/1644423353-17859-1-git-send-email-fabrice.gasnier@foss.st.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>