rmmod: fix bad error message

    Before:

    ># busybox_old rmmod gtrhfhdfghdf
    rmmod: can't unload 'gtrhfhdfghdf': unknown symbol in module, or unknown parameter

    After:

    ># busybox rmmod gtrhfhdfghdf
    rmmod: can't unload module 'gtrhfhdfghdf': No such file or directory

function                                             old     new   delta
modprobe_main                                        726     721      -5
do_modprobe                                          599     590      -9
rmmod_main                                           187     169     -18
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/3 up/down: 0/-32)             Total: -32 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/modutils/rmmod.c b/modutils/rmmod.c
index f13ff9e..5c353ef 100644
--- a/modutils/rmmod.c
+++ b/modutils/rmmod.c
@@ -28,7 +28,7 @@
 int rmmod_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int rmmod_main(int argc UNUSED_PARAM, char **argv)
 {
-	int n;
+	int n, err;
 	unsigned flags = O_NONBLOCK | O_EXCL;
 
 	/* Parse command line. */
@@ -40,7 +40,8 @@
 		flags |= O_TRUNC;
 	if (n & 4) {
 		/* Unload _all_ unused modules via NULL delete_module() call */
-		if (bb_delete_module(NULL, flags) != 0 && errno != EFAULT)
+		err = bb_delete_module(NULL, flags);
+		if (err && err != EFAULT)
 			bb_perror_msg_and_die("rmmod");
 		return EXIT_SUCCESS;
 	}
@@ -58,9 +59,10 @@
 			safe_strncpy(modname, bname, MODULE_NAME_LEN);
 		else
 			filename2modname(bname, modname);
-		if (bb_delete_module(modname, flags))
-			bb_error_msg_and_die("can't unload '%s': %s",
-					modname, moderror(errno));
+		err = bb_delete_module(modname, flags);
+		if (err)
+			bb_perror_msg_and_die("can't unload module '%s'",
+					modname);
 	}
 
 	return EXIT_SUCCESS;