[SCSI] hpsa: removed unneeded structure member max_sg_entries and fix badly named constant MAXSGENTRIES

We had both h->max_sg_entries and h->maxsgentries in the per controller
structure which is terribly confusing.  max_sg_entries was really
just a constant, 32, which defines how big the "block fetch table"
is, which is as large as the max number of SG elements embedded
within a command (excluding SG elements in chain blocks).

MAXSGENTRIES was the constant used to denote the max number of SG
elements embedded within a command, also a poor name.

So renamed MAXSGENTREIS to SG_ENTRIES_IN_CMD, and removed
h->max_sg_entries and replaced it with SG_ENTRIES_IN_CMD.

h->maxsgentries is unchanged, and is the maximum number of sg
elements the controller will support in a command, including
those in chain blocks, minus 1 for the chain block pointer..
Signed-off-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>