cciss: fix proc warning on attempt to remove non-existant directory

Randy reports that he gets the following stack trace when
removing the cciss module:

[  109.164277] Pid: 3463, comm: rmmod Not tainted 2.6.37-rc1 #7
[  109.164280] Call Trace:
[  109.164292]  [<ffffffff8107eb8d>] warn_slowpath_common+0xc6/0xf3
[  109.164299]  [<ffffffff8107ecaa>] warn_slowpath_fmt+0x5b/0x6b
[  109.164307]  [<ffffffff8155175b>] ? _raw_spin_unlock+0x40/0x4b
[  109.164313]  [<ffffffff8123dd1e>] remove_proc_entry+0x156/0x35e
[  109.164320]  [<ffffffff812cd91b>] ? do_raw_spin_unlock+0xff/0x10f
[  109.164327]  [<ffffffff8113823d>] ? trace_hardirqs_on+0x10/0x4a
[  109.164333]  [<ffffffff8155162d>] ? _raw_spin_unlock_irq+0x4c/0x7b
[  109.164339]  [<ffffffff8154d4d1>] ? wait_for_common+0x145/0x15e
[  109.164345]  [<ffffffff81075337>] ? default_wake_function+0x0/0x22
[  109.164357]  [<ffffffffa0615a8f>] cciss_cleanup+0xa9/0xc7 [cciss]
[  109.164365]  [<ffffffff810d3cb0>] sys_delete_module+0x2d6/0x368
[  109.164371]  [<ffffffff8155036b>] ? lockdep_sys_exit_thunk+0x35/0x67
[  109.164377]  [<ffffffff810fdfaf>] ? audit_syscall_entry+0x172/0x1a5
[  109.164383]  [<ffffffff815502f5>] ? trace_hardirqs_on_thunk+0x3a/0x3f
[  109.164389]  [<ffffffff8100ea72>] system_call_fastpath+0x16/0x1b
[  109.164394] ---[ end trace 88e8568246ed0b1d ]---

which will happen if you don't actually have an HP CISS adapter,
since it'll do an uncondional removal of a proc directory it
never attempted to create in that case.
Reported-by: Randy Dunlap <randy.dunlap@oracle.com>
Tested-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

drivers/block/cciss.c

@@ -4936,7 +4936,8 @@ static void __exit cciss_cleanup(void)
 		}
 	}
 	kthread_stop(cciss_scan_thread);
-	remove_proc_entry("driver/cciss", NULL);
+	if (proc_cciss)
+		remove_proc_entry("driver/cciss", NULL);
 	bus_unregister(&cciss_bus_type);
 }