ethtool: display all speed values, not just the predefined ones

Some NICs report speeds other than 10, 100, 1000, 10000 to user land.
At least display them properly.

Signed-off-by: Olaf Kirch <okir@suse.de>

------------------------------------------------------------------
diff -ur ethtool-6//ethtool.c speed//ethtool.c
--- ethtool-6.orig/ethtool.c	2009-11-19 08:28:23.000000000 +0100
+++ ethtool-6/ethtool.c	2009-11-19 08:22:46.000000000 +0100
@@ -819,7 +819,7 @@
 		fprintf(stdout, "10000Mb/s\n");
 		break;
 	default:
-		fprintf(stdout, "Unknown! (%i)\n", ethtool_cmd_speed(ep));
+		fprintf(stdout, "%iMb/s\n", ethtool_cmd_speed(ep));
 		break;
 	};