x86: coding style cleanup for kernel/bootflag.c

This patch eliminates checkpatch.pl complaints on bootflag.c

No code changed:

   text    data     bss     dec     hex filename
    321       8       0     329     149 bootflag.o.before
    321       8       0     329     149 bootflag.o.after

   md5:
      9c1b474bcf25ddc1724a29c19880043f  bootflag.o.before.asm
      9c1b474bcf25ddc1724a29c19880043f  bootflag.o.after.asm

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>