cciss: add cciss_allow_hpsa module parameter

Add the cciss_allow_hpsa modules parameter.  This allows users to use the
hpsa driver instead of cciss for older controllers.

Signed-off-by: Mike Miller <mike.miller@hp.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>