usb: dwc2: gadget: manage ep0 state in software

Manage ep0 state in software to add handling of status OUT stage.
Just toggling hsotg->setup in s3c_hsotg_handle_outdone leaves it in
wrong state in 2-stage control transfers.
Moreover, ensure that for setup-packet s3c_hsotg_handle_outdone is
called either from SetupDone or OutDone but not both. Dwc2 ip v3.00a
generates both SetupDone and OutDone on setup packets.

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>