usb: otg: add usb_otg_caps structure for otg capabilities

This patch adds a structure usb_otg_caps to cover all otg related
capabilities of the device, including otg revision, and if hnp/srp/adp
is supported.

Signed-off-by: Li Jun <jun.li@freescale.com>
Reviewed-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>