.i is an ending used for preprocessed stuff.

This patch therefore renames assembler include files to .h and guards
the contents with an #ifdef __ASSEMBLY__.

[ tglx: arch/x86 adaptation ]
Signed-off-by: NAdrian Bunk <bunk@kernel.org>
Signed-off-by: NAndi Kleen <ak@suse.de>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>