usb: gadget: core: fix ->udc_set_speed() logic

usb: gadget: core: fix ->udc_set_speed() logic

Consider the following case: udc controller supports SuperSpeed.  If we
first load a HighSpeed gadget followed by a SuperSpeed gadget, the
SuperSpeed gadget will be limited to HighSpeed as UDC core driver
doesn't call ->udc_set_speed() in the second case.

Call ->udc_set_speed() unconditionally to fix this issue.

This will also fix the case for dwc3 controller driver when SuperSpeed
gadget is loaded first and works in HighSpeed only as udc_set_speed()
was never being called.

Fixes: 6099eca796ae ("usb: gadget: core: introduce ->udc_set_speed() method")
Cc: <stable@vger.kernel.org> [v4.13+]
Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>