Add OpenBIOS as a submodule

Update OpenBIOS images to r1047 built from submodule.

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
diff --git a/.gitmodules b/.gitmodules
index 7884471..c3faa38 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -10,3 +10,6 @@
 [submodule "roms/ipxe"]
 	path = roms/ipxe
 	url = git://git.qemu.org/ipxe.git
+[submodule "roms/openbios"]
+	path = roms/openbios
+	url = git://git.qemu.org/openbios.git