Update to SeaBIOS 0.5.0

The only change is updating the makefile but that way we're carrying an official
release.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
(cherry picked from commit eac1bb74be4d95616b8a6217e020b1b0d6918608)
diff --git a/pc-bios/bios.bin b/pc-bios/bios.bin
index d76f678..827327d 100644
--- a/pc-bios/bios.bin
+++ b/pc-bios/bios.bin
Binary files differ
diff --git a/roms/seabios b/roms/seabios
index c4c9fae..494302f 160000
--- a/roms/seabios
+++ b/roms/seabios
@@ -1 +1 @@
-Subproject commit c4c9fae1ba486a5be754d0a41ef1be9d2aef77c9
+Subproject commit 494302fe196f7016d56814f0adc83ba1d54c0518