usb: gadget: s3c-hsotg: fix "halted" property updating

Property "halted" of s3c_hsotg_ep structure is actually initialised when ep
enabled, and changed when halt is set/cleared.

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>