No CLOCK_MONOTONIC_RAW on OpenBSD.

Index: libweston/backend.h
--- libweston/backend.h.orig
+++ libweston/backend.h
@@ -33,9 +33,7 @@
 #define LIBWESTON_BACKEND_INTERNAL_H
 
 #define WESTON_PRESENTATION_CLOCKS_SOFTWARE \
-	((1 << CLOCK_MONOTONIC) | \
-	 (1 << CLOCK_MONOTONIC_RAW) | \
-	 (1 << CLOCK_MONOTONIC_COARSE))
+	(1 << CLOCK_MONOTONIC)
 
 struct weston_hdr_metadata_type1;
 
