usb: deprecate the third argument of usb_maxpacket()

usb: deprecate the third argument of usb_maxpacket()

This is a transitional patch with the ultimate goal of changing the
prototype of usb_maxpacket() from:
| static inline __u16
| usb_maxpacket(struct usb_device *udev, int pipe, int is_out)

into:
| static inline u16 usb_maxpacket(struct usb_device *udev, int pipe)

The third argument of usb_maxpacket(): is_out gets removed because it
can be derived from its second argument: pipe using
usb_pipeout(pipe). Furthermore, in the current version,
ubs_pipeout(pipe) is called regardless in order to sanitize the is_out
parameter.

In order to make a smooth change, we first deprecate the is_out
parameter by simply ignoring it (using a variadic function) and will
remove it later, once all the callers get updated.

The body of the function is reworked accordingly and is_out is
replaced by usb_pipeout(pipe). The WARN_ON() calls become unnecessary
and get removed.

Finally, the return type is changed from __u16 to u16 because this is
not a UAPI function.

Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Link: https://lore.kernel.org/r/20220317035514.6378-2-mailhol.vincent@wanadoo.fr
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>