seabios: use correct submodule hash

Commit 392ecf54 introduced an accidental change
to the roms/seabios submodule.  This commit partially reverts that commit to
ensure the seabios module points to the right commit.
Reported-by: NMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

seabios @ 5da68339

-Subproject commit 8362699269d7b3c816981be0e306d7531aa3ea1d
+Subproject commit 5da68339ecf44677b8f4f115cdf3cb1da46a9f6c