usb: gadget: apply generic altsetting support check mechanism

Replace calls of gadget_supports_altsettings() function (which check altset
support by comparing UDC controller name with hardcoded names) with
gadget_is_altset_supported() which checks generic quirk bitfield.

Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>