x86: Fix kexec reservation

The reservation of space for the kexec area in
kexec_reserve_area is incorrect. It specifies the
start address and size to reserve_e820_mem when
the args should be start and end.

Bug found and fixed by Dave Anderson.

Signed-off-by: Bill Burns <bburns@redhat.com>

xen/arch/x86/setup.c

@@ -362,7 +362,7 @@ void __init kexec_reserve_area(struct e820map *e820)
 
     is_reserved = 1;
 
-    if ( !reserve_e820_ram(e820, kdump_start, kdump_size) )
+    if ( !reserve_e820_ram(e820, kdump_start, kdump_start + kdump_size) )
     {
         printk("Kdump: DISABLED (failed to reserve %luMB (%lukB) at 0x%lx)"
                "\n", kdump_size >> 20, kdump_size >> 10, kdump_start);