Mark the C exception handler functions that are directly called through
exception tables visible. LTO needs to know they are accessed from assembler.

[ tglx: Mopped up the wrecked argument alignment. Sigh.... ]
Signed-off-by: NAndi Kleen <ak@linux.intel.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20171222001821.2157-6-andi@firstfloor.org