Fix to-RGB565 conversion helpers to store the result in little-
endian byte order. Update test cases as well.
Signed-off-by: NThomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: NMaíra Canal <mcanal@igalia.com>
Reviewed-by: NJosé Expósito <jose.exposito89@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230102112927.26565-5-tzimmermann@suse.de