x86, printk: Add missing KERN_CONT to NMI selftest

Fix this behaviour:

----------------
| NMI testsuite:
--------------------
  remote IPI:
  ok  |

   local IPI:
  ok  |

Revealed due to a new modification to printk().

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
Link: http://lkml.kernel.org/r/1336492573-17530-3-git-send-email-levinsasha928@gmail.com


Signed-off-by: H. Peter Anvin <hpa@zytor.com>