scsi: megaraid_sas: raid 1 fast path code optimize

No functional change. Code refactor.

Remove function megasas_fpio_to_ldio as we never require to convert fpio
to ldio because of frame unavailability.  Grab extra frame of raid 1
write fast path before it creates first frame as Fast Path.  Removed
is_raid_1_fp_write flag as raid 1 write fast path command is decided
using r1_alt_dev_handle only.  Move resetting megasas_cmd_fusion fields
at common function megasas_return_cmd_fusion.

Signed-off-by: Shivasharan S <shivasharan.srikanteshwara@broadcom.com>
Signed-off-by: Kashyap Desai <kashyap.desai@broadcom.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Tomas Henzl <thenzl@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>