fix FTBS on debian: missing statement after label

Compilers on recent Debian (gcc as well as clang) break compilation if
there's no statement after a label:

> ../../src/r128_driver.c:571:1: error: expected statement
> }

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
Part-of: <https://gitlab.freedesktop.org/xorg/driver/xf86-video-r128/-/merge_requests/12>

src/r128_driver.c

@@ -548,6 +548,7 @@ void R128GetPanelInfoFromBIOS(xf86OutputPtr output)
                    "function properly\n");
     }
     return;
+
 fallback:
 #ifdef WSDISPLAYIO_GINFO
     if ((!r128_output->PanelXRes || !r128_output->PanelYRes) &&
@@ -568,6 +569,7 @@ fallback:
 	}
     }
 #endif
+    return;
 }
 
 /* Read PLL parameters from BIOS block.  Default to typical values if there