usb: gadget: composite: Show warning if function driver's descriptors are incomplete.

In the config_ep_by_speed_and_alt function, select the corresponding
descriptor through g->speed. But some legacy or not well designed
function drivers may not support the corresponding speed. So, we can
directly display warnings instead of causing kernel panic. At the
same time, it indicates the reasons in warning message.

Reviewed-by: Peter Chen <peter.chen@kernel.org>
Signed-off-by: Qihang Hu <huqihang@oppo.com>
Link: https://lore.kernel.org/r/20211110101129.462357-1-huqihang@oppo.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>