headers_check fix: linux/elf-fdpic.h

fix the following 'make headers_check' warning:

  usr/include/linux/elf-fdpic.h:62: extern's make no sense in userspace
Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@gmail.com>

include/linux/elf-fdpic.h

@@ -58,11 +58,13 @@ struct elf_fdpic_params {
 #define ELF_FDPIC_FLAG_PRESENT		0x80000000	/* T if this object is present */
 };
 
+#ifdef __KERNEL__
 #ifdef CONFIG_MMU
 extern void elf_fdpic_arch_lay_out_mm(struct elf_fdpic_params *exec_params,
 				      struct elf_fdpic_params *interp_params,
 				      unsigned long *start_stack,
 				      unsigned long *start_brk);
 #endif
+#endif /* __KERNEL__ */
 
 #endif /* _LINUX_ELF_FDPIC_H */