H750 does not have a HBA mode. Instead you can convert Physical Disks to Non-RAID mode. Refer below link for details on this [URL] 
Hi, I want to switch my PERC H750 from RAID mode to HBA mode, but I didn't find the option to do that !On other versions I think it's supposed to be in : "Controller Management > Advanced Controller Management > Switch to HBA mode". My server is a PowerEdge R740 with 2 x SSD SATA 480GB and 14 x HDD SAS 2.4GB Thank you!
Switch PERC H750 to HBA mode