megaraid_sas: Fix for IO failing post OCR in SRIOV environment

Driver assumes that VFs always have peers present whenever they have
same LD IDs. But this is not the case.  This patch handles the above
mentioned by explicitly checking for a peer before making HA/non-HA path
decision.

Signed-off-by: Uday Lingala <uday.lingala@avagotech.com>
Signed-off-by: Sumit Saxena <sumit.saxena@avagotech.com>
Reviewed-by: Tomas Henzl <thenzl@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>