Initialize the upper 16 bits of the memory sizes properly (to 0).

They were garbage that happened to be 0 in many cases.  (real_to_prot()
happens to leave the value of the real-mode %cr0 in %eax and the
memory-size BIOS calls usually don't touch the upper bits of %eax.
The upper 16 bits of %cr0 are usually 0 at boot time, at least on
486's.

Should be in 2.2.

sys/i386/boot/biosboot/bios.S

@@ -24,7 +24,7 @@
  * the rights to redistribute these changes.
  *
  *	from: Mach, Revision 2.2  92/04/04  11:34:26  rpd
- *	$Id: bios.S,v 1.5 1995/09/03 05:36:13 julian Exp $
+ *	$Id: bios.S,v 1.6 1996/11/11 14:03:33 bde Exp $
  */
 
 /*
@@ -352,12 +352,13 @@ xext:	movb	$0x88, %ah
 	cli
 
 xdone:
-	mov	%eax, %ebx
+	pushl	$0			/* actually pushw $0 */
+	pushl	%eax			/* actually pushw %ax */
 
 	data32
 	call	EXT(real_to_prot)
 
-	mov	%ebx, %eax
+	pop	%eax
 	pop     %edi
 	pop	%esi
 	pop	%ebx