usb: dwc2: gadget: don't process XferCompl on setup packet

Only process DOEPINT.XferCompl on data packet as DOEPINTn.SetUp can
occur with or without DOEPINT.XferCompl. When DOEPINT.SetUp occurs
with DOEPINT.XferCompl, only DOEPINT.SetUp needs to be handled.

Moreover, ignore DOEPINT.XferCompl when it occurs with
DOEPINT.StupPktRcvd as driver needs to wait for DOEPINT.SetUp to
continue.

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>