mem_class: fix bug

When I build and boot -next on fedora 10, I can not login anymore.
When I input the user name and password, the system does not output
any message and requires user to input the user name and password
again and again.

I find the patch which caused this problem with "GIT BISECT" command.
And the patch is
    commit 7c4b7daa1878972ed0137c95f23569124bd6e2b1
    "mem_class: use minor as index instead of searching the array".

Though I don't know the real reason why user could not login, I
confirmed the patch I made as following could resolve the problem on
fedora 10.
Signed-off-by: Jin Dongming <jin.dongming@np.css.fujitsu.com>
Acked-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/char/mem.c

@@ -878,8 +878,8 @@ static const struct memdev {
 	[ 4] = { "port", &port_fops, NULL },
 #endif
 	[ 5] = { "zero", &zero_fops, &zero_bdi },
-	[ 6] = { "full", &full_fops, NULL },
-	[ 7] = { "random", &random_fops, NULL },
+	[ 7] = { "full", &full_fops, NULL },
+	[ 8] = { "random", &random_fops, NULL },
 	[ 9] = { "urandom", &urandom_fops, NULL },
 	[11] = { "kmsg", &kmsg_fops, NULL },
 #ifdef CONFIG_CRASH_DUMP