New core functions to make sending/receiving USB control messages easier
and saner.

In discussions, it turns out that the large majority of users of
usb_control_msg() do so in potentially incorrect ways.  The most common
issue is where a "short" message is received, yet never detected
properly due to "incorrect" error handling.

Handle all of this in the USB core with two new functions to try to make
working with USB control messages simpler.

No more need for dynamic data, messages can be on the stack, and only
"complete" send/receive will work without causing an error.

Link: https://lore.kernel.org/r/20200914153756.3412156-3-gregkh@linuxfoundation.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>