hpsa: add ioaccel sg chaining for the ioaccel2 path

Increase the request size for ioaccel2 path.

The error, if any, returned by hpsa_allocate_ioaccel2_sg_chain_blocks
to hpsa_alloc_ioaccel2_cmd_and_bft should be returned upstream rather
than assumed to be -ENOMEM.

This differs slightly from hpsa_alloc_ioaccel1_cmd_and_bft,
which does not call another hpsa_allocate function and only
has -ENOMEM to return from some kmalloc calls.

Reviewed-by: Scott Teel <scott.teel@pmcs.com>
Reviewed-by: Kevin Barnett <kevin.barnett@pmcs.com>
Signed-off-by: Robert Elliott <elliott@hp.com>
Signed-off-by: Don Brace <don.brace@pmcs.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: James Bottomley <JBottomley@Odin.com>