anv: add MAP_POPULATE fallback define for portability

FreeBSD does not have MAP_POPULATE

Reviewed-by: Eric Engestrom <eric.engestrom@intel.com>

src/intel/vulkan/anv_allocator.c

@@ -50,6 +50,10 @@
 #define VG_NOACCESS_WRITE(__ptr, __val) (*(__ptr) = (__val))
 #endif
 
+#ifndef MAP_POPULATE
+#define MAP_POPULATE 0
+#endif
+
 /* Design goals:
  *
  *  - Lock free (except when resizing underlying bos)