usb: gadget: udc: core: Prevent redundant calls to pullup

usb_gadget_connect calls gadget->ops->pullup without checking whether
gadget->connected was previously set. Make this symmetric to
usb_gadget_disconnect by returning early if gadget->connected is
already set.

Fixes: 5a1da544

 ("usb: gadget: core: do not try to disconnect gadget if it is not connected")
Cc: stable@vger.kernel.org
Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
Link: https://lore.kernel.org/r/20230407030741.3163220-2-badhri@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>