x86: coding style fixes to arch/x86/kernel/sys_x86_64.c

Fix all errors and many warnings reported by checkpatch.pl
without change sys_x86_64.o

arch/x86/kernel/sys_x86_64.o:
text    data     bss     dec     hex filename
1567       0       0    1567     61f sys_x86_64.o.after
1567       0       0    1567     61f sys_x86_64.o.before
md5:
de28ffedcb5851dfd7ec87a03afec1fd  sys_x86_64.o.after
de28ffedcb5851dfd7ec87a03afec1fd  sys_x86_64.o.before

Signed-off-by: Gustavo F. Padovan <gustavo@las.ic.unicamp.br>
Signed-off-by: Ingo Molnar <mingo@elte.hu>