usb: gadget: composite Allow for larger configuration descriptors

The composite framework allows us to create gadgets composed from many
different functions, which need to fit into a single configuration
descriptor.

Some functions (like uvc) can produce configuration descriptors upwards
of 2500 bytes on their own.

This patch increases the limit from 1024 bytes to 4096.

Signed-off-by: Joel Pepper <joel.pepper@rwth-aachen.de>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>