[SCSI] sd: Reduce buffer size for vpd request

Somehow older areca firmware versions have issues with
scsi_get_vpd_page() and a large buffer, the firmware
seems to crash and the scsi error-handler will start endless
recovery retries.
Limiting the buf-size to 64-bytes fixes this issue with older
firmware versions (<1.49 for my controller).

Fixes a regression with areca controllers and older firmware versions
introduced by commit: 66c28f97

Reported-by: Nix <nix@esperi.org.uk>
Tested-by: Nix <nix@esperi.org.uk>
Signed-off-by: Bernd Schubert <bernd.schubert@itwm.fraunhofer.de>
Cc: stable@vger.kernel.org # delay inclusion for 2 months for testing
Acked-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>