We must unregister from SCSI before we unmap device resources and unhook
the IRQ handler.  Otherwise, SCSI may send us more requests, and we won't
be able to handle them.

I see the following oops during every reboot of my HP DL360:

    ...
    Unmounting local filesystems...done.
    Rebooting... Completed flushing cache on controller 0
    BUG: unable to handle kernel paging request at virtual address f8808040
     printing eip:
    c02dc72b
    *pde = 02120067
    *pte = 00000000
    Oops: 0002 [#1]
    SMP
    Modules linked in:
    CPU:    1
    EIP:    0060:[<c02dc72b>]    Not tainted VLI
    EFLAGS: 00010046   (2.6.21-rc6 #1)
    EIP is at SA5_submit_command+0xb/0x20
    eax: f8808000   ebx: f7a00000   ecx: f79f0000   edx: 37a00000
    esi: f79f0000   edi: 00000000   ebp: 00000000   esp: dd717a44
    ds: 007b   es: 007b   fs: 00d8  gs: 0000  ss: 0068
    Process khelper (pid: 1427, ti=dd716000 task=c2260a70 task.ti=dd716000)
    Stack: c02df2c0 f7a00000 f7a00000 00d41008 c02df691 00000000 00000010 00000002
	   00000001 f79f0000 f7fff844 c1398420 00000000 00000000 00001000 230a3020
	   69666564 5420656e 50434f49 465f544b 4853554c 44414552 0a312009 66656423
    Call Trace:
     [<c02df2c0>] start_io+0x80/0x120
     [<c02df691>] do_cciss_request+0x331/0x350
     [<c014242a>] mempool_alloc+0x2a/0xe0
     [<c020ad71>] blk_alloc_request+0x61/0x80
     [<c020b02e>] get_request+0x15e/0x1e0
     [<c01595e0>] cache_alloc_refill+0xb0/0x1e0
     [<c021049d>] as_update_rq+0x2d/0x80
     [<c0210d28>] as_add_request+0x68/0x90
     [<c0207f99>] elv_insert+0x119/0x160
     [<c020bd0b>] __make_request+0xcb/0x320
     [<c0122ee0>] lock_timer_base+0x20/0x50
     [<c0123096>] del_timer+0x56/0x60
     [<c020a7b8>] blk_remove_plug+0x38/0x70
     [<c020a815>] __generic_unplug_device+0x25/0x30
     [<c020a835>] generic_unplug_device+0x15/0x30
    ...
Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Acked-by: Mike Miller <mike.miller@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>