cmd_net: drop spurious comma in U_BOOT_CMD

Building for boards that have CONFIG_CMD_CDP enabled fail with:
cmd_net.c:301: error: expected expression before ',' token

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/common/cmd_net.c b/common/cmd_net.c
index 44d17db..b131006 100644
--- a/common/cmd_net.c
+++ b/common/cmd_net.c
@@ -297,7 +297,7 @@
 
 U_BOOT_CMD(
 	cdp,	1,	1,	do_cdp,
-	"Perform CDP network configuration",
+	"Perform CDP network configuration"
 );
 #endif