usb: dwc2: gadget: Do not halt isochronous endpoints

Add a check in dwc2_hsotg_ep_sethalt() so that it does not halt
isochronous endpoints.

Signed-off-by: Vahram Aharonyan <vahrama@synopsys.com>
Signed-off-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>