[SeaBIOS] SeaBIOS doesn't boot from secondary hard drive with OS if primary hard drive is empty

[Аладышев Константин]

When I have 2 SATA disks attached to my board, and only second priority
device is with OS, SeaBIOS doesn't boot.

The "empty" disk doesn't have MBR, so SeaBIOS doesn't stuck on it, it goes
to the end message "No bootable device.  Retrying in 60 seconds."

But if I manually press "ESC" and choose correct disk in interactive promt,
system boots successfully.

Two logs attached to the message (with and without "ESC" interaction). I use
SeaBIOS (d7adf6044a4c772b497e97272adf97426b34a249) as a payload to coreboot.