usb: dwc2: gadget: fix error path in dwc2_gadget_init

In the error path, s3c_hsotg_phy_disable should be called after a
call to s3c_hsotg_phy_enable is made.

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>