cciss: separate error processing and command retrying code in sendcmd_withirq_core()

Separate the error processing from sendcmd_withirq_core from the code
which retries commands.  The rationale for this is that the SCSI error
handling code can then be made to use sendcmd_withirq_core, but avoid
retrying commands.

Signed-off-by: Stephen M. Cameron <scameron@beardog.cca.cpqcorp.net>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>