USB: gadget: Add test mode support for ci13xxx_udc

Implement the test modes mentioned in 7.1.20 section of USB 2.0
specification.  High-speed capable devices must support these test
modes to facilitate compliance testing.

Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>