x86: traps.c declare functions before they get used

Impact: cleanup

 In asm/traps.h :-
 do_double_fault : added under X86_64
 sync_regs : added under X86_64
 math_error : moved out from X86_32 as it is common for both 32 and 64 bit
 math_emulate : moved from X86_32 as it is common for both 32 and 64 bit
 smp_thermal_interrupt : added under X86_64
 mce_threshold_interrupt : added under X86_64

Signed-off-by: Jaswinder Singh <jaswinder@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>