x86: setup_trampoline() - fix section mismatch warning

this patch fixes section mismatch warnings (on x86_64 host) in setup_trampoline(),
which was referencing __initdata variables trampoline_data and trampoline_end.

Warning messages:
WARNING: arch/x86/kernel/built-in.o(.cpuinit.text+0x2b6a): Section mismatch in reference from the function setup_trampoline()
to the variable .init.data:trampoline_data
The function __cpuinit setup_trampoline() references
a variable __initdata trampoline_data.
If trampoline_data is only used by setup_trampoline then
annotate trampoline_data with a matching annotation.

WARNING: arch/x86/kernel/built-in.o(.cpuinit.text+0x2b71): Section mismatch in reference from the function setup_trampoline()
to the variable .init.data:trampoline_end
The function __cpuinit setup_trampoline() references
a variable __initdata trampoline_end.
If trampoline_end is only used by setup_trampoline then
annotate trampoline_end with a matching annotation.

Signed-off-by: Ingo Molnar <mingo@elte.hu>