[coreboot] seabios change to boot from last boot device for gPXE or other option rom booting

[Joe Julian]

The hardcoded boot order method when using seabios with coreboot makes 
booting from option roms difficult if the number of hard drives 
installed is not a fixed number. I used this patch to allow choosing the 
last boot device by setting the nibble to 0xf. This allows me to boot 
from the gPXE option rom.

diff --git a/src/boot.c b/src/boot.c
index 6b4e985..44c1665 100644
--- a/src/boot.c
+++ b/src/boot.c
@@ -51,7 +51,8 @@ boot_setup()
     SET_EBDA(boot_sequence, 0xffff);
     if (CONFIG_COREBOOT) {
         // XXX - hardcode defaults for coreboot.
-        IPL.bootorder = 0x00000231;
+        // use 0xf to choose the last bev device
+        IPL.bootorder = 0x0000231f;
         IPL.checkfloppysig = 1;
     } else {
         // On emulators, get boot order from nvram.
@@ -372,6 +373,10 @@ do_boot(u16 seq_nr)
     u32 bootdev = IPL.bootorder;
     bootdev >>= 4 * seq_nr;
     bootdev &= 0xf;
+    if(bootdev == 0x0f) {
+        dprintf(1, "IPL.bevcount = %d)\n", IPL.bevcount);
+        bootdev = IPL.bevcount;
+    }
 
     if (bootdev == 0) {
         printf("No bootable device.\n");