Make -kernel for linux work with bochsbios

While trying to run -kernel with -bios pc-bios/pcbios.bin, I realized
that I was actually writing data to %es, but only set up %ds to a 32-bit
segment we want to write to.

So at the end of the day the data hasn't actually been copied. Oops.

So here's a fix to set ES instead of DS, which makes -kernel work with
BOCHS bios again (and actually makes the code do the correct thing)!
Signed-off-by: NAlexander Graf <agraf@suse.de>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

pc-bios/optionrom/linuxboot.S

@@ -102,11 +102,11 @@ copy_kernel:
 	mov		$1, %eax
 	mov		%eax, %cr0
 
-	/* So we can set DS to a 32-bit segment */
+	/* So we can set ES to a 32-bit segment */
 	mov		$0x10, %eax
-	mov		%eax, %ds
+	mov		%eax, %es
 
-	/* We're now running in 16-bit CS, but 32-bit DS! */
+	/* We're now running in 16-bit CS, but 32-bit ES! */
 
 	/* Load kernel and initrd */
 	read_fw_blob(FW_CFG_KERNEL)
@@ -118,9 +118,9 @@ copy_kernel:
 	mov		$0, %eax
 	mov		%eax, %cr0
 
-	/* DS = CS */
+	/* ES = CS */
 	mov		%cs, %ax
-	mov		%ax, %ds
+	mov		%ax, %es
 
 	jmp		boot_kernel