weston: Fix wayland-protocols dependency

weston: Fix wayland-protocols dependency

An SDK build of weston fails:
```
Run-time dependency wayland-protocols found: NO (tried pkgconfig and cmake)
```

The file wayland-protocols.pc is missing in the SDK. This is traced to
the upgrade of wayland-protocols to 1.38 [1], which re-enables the dev
package, which moves wayland-protocols.pc to wayland-protocols-dev.

[1] https://github.com/openembedded/openembedded-core/commit/5de187aee675a78fe59620a3fb64a5da5ae662aa

Signed-off-by: Tom Hochstein <tom.hochstein@oss.nxp.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>