usb: gadget: configfs: Add a specific configFS reset callback

usb: gadget: configfs: Add a specific configFS reset callback

In order for configFS based USB gadgets to set the proper charge current
for bus reset scenarios, expose a separate reset callback to set the
current to 100mA based on the USB battery charging specification.

Reviewed-by: Peter Chen <peter.chen@nxp.com>
Signed-off-by: Wesley Cheng <wcheng@codeaurora.org>
Link: https://lore.kernel.org/r/1609283011-21997-4-git-send-email-wcheng@codeaurora.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>