x86: fix early-BUG message

The .asciz directive takes any number of strings, but each one is zero-
terminated, and string pasting is not done as in C. That results in only the
first line being output.

Replace .asciz with multiple .ascii directives and terminate with .asciz.

Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>