EDAC/mc_sysfs: Add missing newlines when printing {max,dimm}_location

Reading those sysfs entries gives:

  [root@localhost /]# cat /sys/devices/system/edac/mc/mc0/max_location
  memory 3 [root@localhost /]# cat /sys/devices/system/edac/mc/mc0/dimm0/dimm_location
  memory 0 [root@localhost /]#

Add newlines after the value it prints for better readability.

  [ bp: Make len a signed int and change the check to catch wraparound.
    Increment the pointer p only when the length check passes. Use
    scnprintf(). ]

Signed-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/1600051734-8993-1-git-send-email-wangxiongfeng2@huawei.com