x86: memtest fix use of reserve_early()

Hi all,

Wrong usage of 2nd parameter in reserve_early call.
66/75: reserve_early(start_bad, last_bad - start_bad, "BAD RAM");
                                ^^^^^^^^^^^^^^^^^^^^

The correct way is to use 'end' address and not 'size'.
As a bonus a fix to the printk format.

Signed-off-by: Daniele Calore <orkaan@orkaan.org>
Acked-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>