Input: usbtouchscreen - use guard notation when acquiring mutexes

This makes the code more compact and error handling more robust.

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20240712051851.3463657-7-dmitry.torokhov@gmail.com


Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>