x86: cleanup 64bit unistd.h

sys_iopl is long gone and there is no reason to declare
sys_rt_sigaction here.

Remove it all together and fix the whitespace mess as well.
It's worth the trouble: 25897 -> 21337 bytes, the win is
larger than the memory of my first computer :)
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NIngo Molnar <mingo@elte.hu>