[SCSI] megaraid_sas: check max_sgl reported by FW for setting max_sectors_per_req

1. Setting the max_sectors_per_req based on max SGL supported by the
   FW. Prior versions calculated this value from controller info's
   max_sectors_1, max_sectors_2. For certain controllers/FW, this was
   resulting in a value greater than max SGL supported by the FW. Now
   we take the min of max sgl from FW and max_sectors calculation.

2. Increased MFI_POLL_TIMEOUT_SECS to 60 seconds from 10. FW may take
   a max of 60 seconds to respond to the INIT cmd.

Signed-off-by: Bo Yang <bo.yang@lsi.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>