megaraid_sas: endianness related bug fixes and code optimization

This patch addresses below issues:

1) Few endianness bug fixes.
2) Break the iteration after (MAX_LOGICAL_DRIVES_EXT - 1)),
   instead of MAX_LOGICAL_DRIVES_EXT.
3) Optimization in MFI INIT frame before firing.
4) MFI IO frame should be 256bytes aligned.  Code is optimized to reduce
   the size of frame for fusion adapters and make the MFI frame size
   calculation a bit transparent and readable.

Cc: <stable@vger.kernel.org>
Signed-off-by: Kashyap Desai <kashyap.desai@avagotech.com>
Signed-off-by: Sumit Saxena <sumit.saxena@avagotech.com>
Signed-off-by: Chaitra Basappa <chaitra.basappa@avagotech.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>