scsi: core: Fix a procfs host directory removal regression

scsi_proc_hostdir_rm() decreases a reference counter and hence must only be
called once per host that is removed. This change does not require a
scsi_add_host_with_dma() change since scsi_add_host_with_dma() will return
0 (success) if scsi_proc_host_add() is called.

Fixes: fc663711

 ("scsi: core: Remove the /proc/scsi/${proc_name} directory earlier")
Cc: John Garry <john.g.garry@oracle.com>
Reported-by: John Garry <john.g.garry@oracle.com>
Link: https://lore.kernel.org/all/ed6b8027-a9d9-1b45-be8e-df4e8c6c4605@oracle.com/
Reported-by:  <syzbot+645a4616b87a2f10e398@syzkaller.appspotmail.com>
Link: https://lore.kernel.org/linux-scsi/000000000000890fab05f65342b6@google.com/
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20230307214428.3703498-1-bvanassche@acm.org
Tested-by: John Garry <john.g.garry@oracle.com>
Tested-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>