x86: mark memory_setup __init

Otherwise

WARNING: vmlinux.o(.text+0x64a9): Section mismatch: reference to .init.text:machine_specific_memory_setup (between 'memory_setup' and 'show_cpuinfo')
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/setup_64.c

@@ -279,7 +279,7 @@ static void discover_ebda(void)
 }
 
 /* Overridden in paravirt.c if CONFIG_PARAVIRT */
-void __attribute__((weak)) memory_setup(void)
+void __attribute__((weak)) __init memory_setup(void)
 {
        machine_specific_memory_setup();
 }