correct usage botch.

Reference: /n/atom/patch/applied/msrusage
Date: Sat Oct 24 18:21:50 CES 2015
Signed-off-by: quanstro@quanstro.net

--- /sys/src/cmd/aux/rdmsr.c	Sat Oct 24 18:21:37 2015
+++ /sys/src/cmd/aux/rdmsr.c	Sat Oct 24 18:21:38 2015
@@ -17,7 +17,7 @@
 void
 usage(void)
 {
-	fprint(2, "usage: rdmsr ...\n");
+	fprint(2, "usage: %s [-w machno] msr ...\n", argv0);
 	exits("usage");
 }
 
--- /sys/src/cmd/aux/wrmsr.c	Sat Oct 24 18:21:40 2015
+++ /sys/src/cmd/aux/wrmsr.c	Sat Oct 24 18:21:41 2015
@@ -17,7 +17,7 @@
 void
 usage(void)
 {
-	fprint(2, "usage: %s ...\n", argv0);
+	fprint(2, "usage: %s [-w machno] msr value ...\n", argv0);
 	exits("usage");
 }