mptutil: document that disabled/enabled are also supported

This change officially documents the fact that the `volume cache
enabled` and `volume cache disabled` are also supported.

While here, remove an unnecessary newline at the end of a warn*(3) call.
warn*(3) adds a newline automatically.

MFC after:	1 week

usr.sbin/mptutil/mpt_volume.c

@@ -219,7 +219,8 @@ volume_cache(int ac, char **av)
                 *s1 = tolower(*s1);
 	if ((strcmp(av[2], "enable")) && (strcmp(av[2], "enabled")) &&
 	    (strcmp(av[2], "disable")) && (strcmp(av[2], "disabled"))) {
-		warnx("volume cache: invalid flag, must be 'enable' or 'disable'\n");
+		warnx("volume cache: invalid flag; "
+		    "must be 'enable', 'enabled', 'disable', or 'disabled'");
 		return (EINVAL);
 	}
 

usr.sbin/mptutil/mptutil.8

@@ -29,7 +29,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd August 16, 2009
+.Dd May 24, 2024
 .Dt MPTUTIL 8
 .Os
 .Sh NAME
@@ -71,7 +71,7 @@
 .Nm
 .Op Fl u Ar unit
 .Cm volume cache Ar volume
-.Ar enable|disable
+.Ar enable|enabled|disable|disabled
 .Nm
 .Op Fl u Ar unit
 .Cm clear
@@ -239,7 +239,7 @@ Sets the name of
 .Ar volume
 to
 .Ar name .
-.It Cm volume cache Ar volume Ar enable|disable
+.It Cm volume cache Ar volume Ar enable|enabled|disable|disabled
 Enables or disables the drive write cache for the member drives of
 .Ar volume .
 .It Cm volume status Ar volume