usb: dwc2: gadget: dont warn if endpoint is not enabled

The warning is probably good but it has false positives in both dma and non-dma
cases. So its not very helpful in either.

Tested-by: Robert Baldyga <r.baldyga@samsung.com>
Acked-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Mian Yousaf Kaukab <yousaf.kaukab@intel.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>