sh: return_address: Add missing #include <asm/ftrace.h>

arch/sh/kernel/return_address.c:49:7: warning: no previous prototype for ‘return_address’ [-Wmissing-prototypes]

Signed-off-by: Geert Uytterhoeven <[e-mail]>
Reviewed-by: John Paul Adrian Glaubitz <[e-mail]>
Link: https://lore.kernel.org/r/45685[e-mail]
Signed-off-by: John Paul Adrian Glaubitz <[e-mail]>

arch/sh/kernel/return_address.c

···
  */
 #include <linux/kernel.h>
 #include <linux/module.h>
+
 #include <asm/dwarf.h>
+#include <asm/ftrace.h>
 
 #ifdef CONFIG_DWARF_UNWINDER