wayland: update 1.20.0 -> 1.21.0

Drop the patch, as it is no longer necessary
(genereated .pc defines everything as relative to the .pc path).

Signed-off-by: Alexander Kanavin <alex@linutronix.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>