cciss: Dynamically allocate the drive_info_struct for each logical drive.

cciss: Dynamically allocate the drive_info_struct for each logical drive.
This reduces the size of the per-hba ctlr_info structure from 106936
bytes to 8132 bytes.  That's on 32-bit systems.  On 64-bit systems, the
improvement is even bigger.  Without this, the ctlr_info struct is so big
that the driver won't even load on a 64 bit system if CISS_MAX_LUN was
at it's current setting of 1024 logical drives.

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