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: NIngo Molnar <mingo@elte.hu>

arch/x86/kernel/trampoline_64.S

@@ -32,7 +32,7 @@
 
 /* We can free up trampoline after bootup if cpu hotplug is not supported. */
 #ifndef CONFIG_HOTPLUG_CPU
-.section .init.data, "aw", @progbits
+.section .cpuinit.data, "aw", @progbits
 #else
 .section .rodata, "a", @progbits
 #endif