USB: gadget: MIPS ci13xxx_udc

MIPS USB IP core family device controller
Currently it only supports IP part number CI13412.

[dbrownell@users.sourceforge.net: minor comment tweaks]

Signed-off-by: David Lopo <dlopo@chipidea.mips.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>