usb: dwc2: Add safety check in setting of descriptor chain pointers

In some cases device sending ZLP IN on non EP0 which
reassigning EP0 OUT descriptor pointer to that EP.
Dedicated for EP0 OUT descriptor multiple time re-used by
other EP while that descriptor already in use by EP0 OUT
for SETUP transaction. As result when SETUP packet received
BNA interrupt asserting.

In dwc2_hsotg_program_zlp() function dwc2_gadget_set_ep0_desc_chain()
must be called only for EP0.

Acked-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Minas Harutyunyan <hminas@synopsys.com>
Signed-off-by: Grigor Tovmasyan <tovmasya@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>