seabios: use correct submodule hash

Commit 392ecf543dd2b219828374850d833296a55567ea 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: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

diff --git a/roms/seabios b/roms/seabios
index 8362699..5da6833 160000 (submodule)
--- a/roms/seabios
+++ b/roms/seabios
@@ -1 +1 @@
-Subproject commit 8362699269d7b3c816981be0e306d7531aa3ea1d
+Subproject commit 5da68339ecf44677b8f4f115cdf3cb1da46a9f6c