x86: make setup_xstate_init() __init

WARNING: vmlinux.o(.text+0x22453): Section mismatch in reference from the function setup_xstate_init() to the function .init.text:__alloc_bootmem()
The function setup_xstate_init() references the function __init __alloc_bootmem().
This is often because setup_xstate_init lacks a __init annotation or the annotation of __alloc_bootmem is wrong.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/xsave.c

@@ -272,7 +272,7 @@ void __cpuinit xsave_init(void)
 /*
  * setup the xstate image representing the init state
  */
-void setup_xstate_init(void)
+static void __init setup_xstate_init(void)
 {
 	init_xstate_buf = alloc_bootmem(xstate_size);
 	init_xstate_buf->i387.mxcsr = MXCSR_DEFAULT;