x86: Fix emulation of DIV instruction. Never actually used currently,

but this will avoid a #DE in Xen.
Signed-off-by: Keir Fraser <keir@xensource.com>

xen/arch/x86/x86_emulate.c

@@ -586,7 +586,7 @@ static int imul_dbl(unsigned long m[2])
  */
 static int div_dbl(unsigned long u[2], unsigned long v)
 {
-    if ( (v == 0) || (u[1] > v) || ((u[1] == v) && (u[0] != 0)) )
+    if ( (v == 0) || (u[1] >= v) )
         return 1;
     asm ( "div %4"
           : "=a" (u[0]), "=d" (u[1])