usb:hsotg:samsung: Determine number of EPs from HW configuration register

This commit adds support for determining of EPs number during run time.

Configuration is read from a HW configuration register in a specially
created s3c_hsotg_hw_cfg function.

Moreover it was necessary to defer at probe allocation of the
struct s3c_hsotg_ep instances until number of endpoints is known.

Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>