[SCSI] remove scsi_cmnd->state

[SCSI] remove scsi_cmnd->state

We never look at it except for the old megaraid driver that abuses it
for sending internal commands.  That usage can be fixed easily because
those internal commands are single-threaded by a mutex and we can easily
use a completion there.

Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>