fbdev: fix /proc/fb oops after module removal

/proc/fb is not removed during rmmod.

Steps to reproduce:

	modprobe fb
	rmmod fb
	ls /proc

BUG: unable to handle kernel paging request at ffffffffa0094370
IP: [<ffffffff802b92a1>] proc_get_inode+0x101/0x130
PGD 203067 PUD 207063 PMD 17e758067 PTE 0
Oops: 0000 [1] SMP
last sysfs file: /sys/devices/pci0000:00/0000:00:1e.0/0000:05:02.0/resource
CPU 1
Modules linked in: nf_conntrack_irc xt_state iptable_filter ipt_MASQUERADE iptable_nat nf_nat nf_conntrack_ipv4 nf_conntrack ip_tables x_tables vfat fat usbhid ehci_hcd uhci_hcd usbcore sr_mod cdrom [last unloaded: fb]
Pid: 21205, comm: ls Not tainted 2.6.25-rc8-mm2 #14
RIP: 0010:[<ffffffff802b92a1>]  [<ffffffff802b92a1>] proc_get_inode+0x101/0x130
RSP: 0018:ffff81017c4bfc78  EFLAGS: 00010246
RAX: 0000000000008000 RBX: ffff8101787f5470 RCX: 0000000048011ccc
RDX: ffffffffa0094320 RSI: ffff810006ad43b0 RDI: ffff81017fc2cc00
RBP: ffff81017e450300 R08: 0000000000000002 R09: ffff81017c5d1000
R10: 0000000000000000 R11: 0000000000000246 R12: ffff81016b903a28
R13: ffff81017f822020 R14: ffff81017c4bfd58 R15: ffff81017f822020
FS:  00007f08e71696f0(0000) GS:ffff81017fc06480(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: ffffffffa0094370 CR3: 000000017e54a000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process ls (pid: 21205, threadinfo ffff81017c4be000, task ffff81017de48770)
Stack:  ffff81017c5d1000 00000000ffffffea ffff81017e450300 ffffffff802bdd1e
 ffff81017f802258 ffff81017c4bfe48 ffff81016b903a28 ffff81017f822020
 ffff81017c4bfd48 ffffffff802b9ba0 ffff81016b903a28 ffff81017f802258
Call Trace:
 [<ffffffff802bdd1e>] ? proc_lookup_de+0x8e/0x100
 [<ffffffff802b9ba0>] ? proc_root_lookup+0x20/0x60
 [<ffffffff802882a7>] ? do_lookup+0x1b7/0x210
 [<ffffffff8028883d>] ? __link_path_walk+0x53d/0x7f0
 [<ffffffff80295eb8>] ? mntput_no_expire+0x28/0x130
 [<ffffffff80288b4a>] ? path_walk+0x5a/0xc0
 [<ffffffff80288dd3>] ? do_path_lookup+0x83/0x1c0
 [<ffffffff80287785>] ? getname+0xe5/0x210
 [<ffffffff80289adb>] ? __user_walk_fd+0x4b/0x80
 [<ffffffff8028236c>] ? vfs_lstat_fd+0x2c/0x70
 [<ffffffff8028bf1e>] ? filldir+0xae/0xf0
 [<ffffffff802b92e9>] ? de_put+0x9/0x50
 [<ffffffff8029633d>] ? mnt_want_write+0x2d/0x80
 [<ffffffff8029339f>] ? touch_atime+0x1f/0x170
 [<ffffffff802b9b1d>] ? proc_root_readdir+0x7d/0xa0
 [<ffffffff802825e7>] ? sys_newlstat+0x27/0x50
 [<ffffffff8028bffb>] ? vfs_readdir+0x9b/0xd0
 [<ffffffff8028c0fe>] ? sys_getdents+0xce/0xe0
 [<ffffffff8020b39b>] ? system_call_after_swapgs+0x7b/0x80

Code: b7 83 b2 00 00 00 25 00 f0 00 00 3d 00 80 00 00 74 19 48 89 93 f0 00 00 00 48 89 df e8 39 9a fd ff 48 89 d8 48 83 c4 08 5b 5d c3 <48> 83 7a 50 00 48 c7 c0 60 16 45 80 48 c7 c2 40 17 45 80 48 0f
RIP  [<ffffffff802b92a1>] proc_get_inode+0x101/0x130
 RSP <ffff81017c4bfc78>
CR2: ffffffffa0094370
---[ end trace c71hiarjan8ab739 ]---

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
"Antonino A. Daplas" <adaplas@pol.net>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>