x86, mm: Set memblock initial limit to 1M

memblock_x86_fill() could double memory array.
If we set memblock.current_limit to 512M, so memory array could be around 512M.
So kdump will not get big range (like 512M) under 1024M.

Try to put it down under 1M, it would use about 4k or so, and that is limited.
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1353123563-3103-10-git-send-email-yinghai@kernel.orgSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>

arch/x86/kernel/setup.c

@@ -890,7 +890,7 @@ void __init setup_arch(char **cmdline_p)
 
 	cleanup_highmap();
 
-	memblock.current_limit = get_max_mapped();
+	memblock.current_limit = ISA_END_ADDRESS;
 	memblock_x86_fill();
 
 	/*