r600g: Silence 'control reaches end of non-void function' warning.

Fixes this GCC warning.
r600_hw_states.c: In function 'r600_translate_fill':
r600_state_inlines.h:136: warning: control reaches end of non-void function

src/gallium/drivers/r600/r600_state_inlines.h

@@ -132,6 +132,9 @@ static INLINE uint32_t r600_translate_fill(uint32_t func)
 		return 1;
 	case PIPE_POLYGON_MODE_POINT:
 		return 0;
+	default:
+		assert(0);
+		return 0;
 	}
 }