usb: s3c-hsotg: do not disconnect gadget when receiving ErlySusp intr

DWC2 databook indicates if the core sets "ErlySusp" bit, an idle state has been
detected on the USB for 3 ms. This situation can be occurred when waiting
a request from user daemon. So, we should keep the connection between udc and
gadget even though this interrupt is occurred.

Signed-off-by: Chanho Park <chanho61.park@samsung.com>
Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>