x86/mm: Mark free_initrd_mem() as __init

... matching various other architectures.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Link: http://lkml.kernel.org/r/4FDF1F5C020000780008A661@nat28.tlf.novell.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/mm/init.c

@@ -385,7 +385,7 @@ void free_initmem(void)
 }
 
 #ifdef CONFIG_BLK_DEV_INITRD
-void free_initrd_mem(unsigned long start, unsigned long end)
+void __init free_initrd_mem(unsigned long start, unsigned long end)
 {
 	/*
 	 * end could be not aligned, and We can not align that,