[SCSI] megaraid_sas: addded support for big endian architecture

This patch will add big endian architecture support to megaraid_sas
driver. The support added is for LSI MegaRAID all generation controllers-
(3Gb/s, 6Gb/s and 12 Gb/s controllers).

We have done basic sanity test @ppc64 arch and @x86_64. Additional
testing/observations are welcome.

[jejb: fix up rejections]
Signed-off-by: Kashyap Desai <kashyap.desai@lsi.com>
Signed-off-by: Sumit Saxena <sumit.saxena@lsi.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>