USB: gadget: validate interface OS descriptor requests

commit 75e5b4849b81e19e9efe1654b30d7f3151c33c2c upstream.

Stall the control endpoint in case provided index exceeds array size of
MAX_CONFIG_INTERFACES or when the retrieved function pointer is null.

Signed-off-by: Szymon Heidrich <szymon.heidrich@gmail.com>
Cc: stable@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>