i386: setup_trampoline() must be __cpuinit

WARNING: arch/i386/kernel/built-in.o(.text+0xf201): Section mismatch: reference to .init.data:trampoline_end (between 'setup_trampoline' and 'cpu_coregroup_map')
WARNING: arch/i386/kernel/built-in.o(.text+0xf207): Section mismatch: reference to .init.data:trampoline_data (between 'setup_trampoline' and 'cpu_coregroup_map')
WARNING: arch/i386/kernel/built-in.o(.text+0xf21a): Section mismatch: reference to .init.data:trampoline_data (between 'setup_trampoline' and 'cpu_coregroup_map')

Harmless but annoying warnings present when building an i386 SMP kernel
with CONFIG_HOTPLUG_CPU=n and gcc < 4.0 .

[ tglx: arch/x86 adaptation ]

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>