mpt2sas, mpt3sas: fix upper bound for the module parameter max_sgl_entries

Change Set:

1. Extended the upper boundary restriction for the module parameter
   max_sgl_entries. Earlier, the max_sgl_entries was capped at the
   SCSI_MAX_SG_SEGMENTS kernel definition. With this change, the user
   would be able to set the max_sgl_entries to any value which is
   greater than SCSI_MAX_SG_SEGMENTS and less than the minimum of
   SCSI_MAX_SG_CHAIN_SEGMENTS & hardware limit (Calculated using
   IOCFacts's MaxChainDepth).

2. Added a print for the message log whenever the user sets the
   max_sgl_entries to a value greater than SCSI_MAX_SG_SEGMENTS to
   warn about the kernel definition overriding.

Signed-off-by: Sreekanth Reddy <Sreekanth.Reddy@avagotech.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>