travis: add missing wayland-protocols

travis: add missing wayland-protocols

> checking for WAYLAND... no
>
> configure: error: Package requirements (wayland-client >= 1.11 wayland-server >= 1.11 wayland-protocols >= 1.8) were not met:
>
> No package 'wayland-protocols' found
>
> Consider adjusting the PKG_CONFIG_PATH environment variable if you
> installed software in a non-standard prefix.
>
> Alternatively, you may set the environment variables WAYLAND_CFLAGS
> and WAYLAND_LIBS to avoid the need to call pkg-config.
> See the pkg-config man page for more details.

Also, added extra path to PKG_CONFIG_PATH env variable.

Fixes: 02cc359372 ("egl/wayland: Use linux-dmabuf interface for buffers")
Signed-off-by: Andres Gomez <agomez@igalia.com>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>