usb: gadget: composite: let USB functions process ctrl reqs in cfg0

It can sometimes be necessary for gadget drivers to process non-standard
control requests, which host devices can send without having sent
USB_REQ_SET_CONFIGURATION.

Therefore, the req_match() usb_function method is enhanced with the new
parameter "config0". When a USB configuration is active, this parameter
is false. When a non-core control request is processed in
composite_setup(), without an active configuration, req_match() of the
USB functions of all available configurations which implement this
function, is called with config0=true. Then the control request gets
processed by the first usb_function instance whose req_match() returns
true.

Signed-off-by: Felix Hädicke <felixhaedicke@web.de>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>