arm: mvebu: sata_mv: Add bootstd hook to enable sata_bootdev

Add hook in sata_mv probe to enable bootstd bootdev.

Note: bootdev_setup_for_sibling_blk() invocation is a noop if bootsd is
not enabled for ahci sata yet.

Signed-off-by: Tony Dinh <mibodhi@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Stefan Roese <sr@denx.de>