usb: gadget: s3c-hsotg: add isochronous transfers support

This patch adds isochronous transfer support. It adds few modifications:
- Modify s3c_hsotg_epint() function. Some interrupts are ignored for
  isochronous endpoints, (e.g. INTknTXFEmpMsk) becouse isochronous request is
  always transfered in single transaction, which ends with XferCompl interrupt.
- Add Odd/Even microframe toggle to allow data transfering in each microframe
  in s3c_hsotg_epint() function.
- Fix s3c_hsotg_ep_enable() function by supporting isochronous endpoint type.

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>