scsi: megaraid_sas: NVMe passthrough command support

NVMe passthrough via MFI interface. Current MegaRAID product supports
different types of encapsulation via the MFI framework.

NVMe native command should be framed by application and it should be
embedded in MFI as payload. The driver will provide interface to send
the MFI frame along with the payload (in this case, payload is NVMe
native command) to the firmware. Driver already has an existing, similar
interface for SATA and SMP passthrough.

1. Driver will pass MFI command to the firmware if the latter supports
   NVMe encapsulated processing (not all SAS3.5 firmware supports this
   feature).

2. Driver exposes sysfs entry support_nvme_encapsulation. This is
   required for backward compatibility for applications using earlier
   driver versions that did not process IOCTL frames and could result in
   host hang.

   This is already fixed as part of commit 82add4e1 ("scsi:
   megaraid_sas: Incorrect processing of IOCTL frames for SMP/STP
   commands")

[mkp: clarified commit message]

Signed-off-by: Sumit Saxena <sumit.saxena@broadcom.com>
Signed-off-by: Shivasharan S <shivasharan.srikanteshwara@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>