radeong: Make is_r3xx inline to avoid warnings.

Split from Marek's immd-mode patch.
diff --git a/src/gallium/winsys/drm/radeon/core/radeon_drm.h b/src/gallium/winsys/drm/radeon/core/radeon_drm.h
index ddd7983..077388e 100644
--- a/src/gallium/winsys/drm/radeon/core/radeon_drm.h
+++ b/src/gallium/winsys/drm/radeon/core/radeon_drm.h
@@ -81,7 +81,7 @@
 /* Guess at whether this chipset should use r300g.
  *
  * I believe that this check is valid, but I haven't been exhaustive. */
-static boolean is_r3xx(int pciid)
+static INLINE boolean is_r3xx(int pciid)
 {
     return (pciid > 0x3150) && (pciid < 0x796f);
 }