powerpc/module_64: Consolidate ftrace code

module_trampoline_target() is only used by ftrace. Move the prototype
within the appropriate #ifdef in the header. Also, move the function
body to the end of module_64.c so as to consolidate all ftrace code in
one place.

No functional changes.

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/2527351f65c53c5866068ae130dc34c5d4ee8ad9.1587488954.git.naveen.n.rao@linux.vnet.ibm.com

arch/powerpc/include/asm/module.h

@@ -90,12 +90,9 @@ struct mod_arch_specific {
 #    ifdef MODULE
 	asm(".section .ftrace.tramp,\"ax\",@nobits; .align 3; .previous");
 #    endif	/* MODULE */
-#endif
 
 int module_trampoline_target(struct module *mod, unsigned long trampoline,
 			     unsigned long *target);
-
-#ifdef CONFIG_DYNAMIC_FTRACE
 int module_finalize_ftrace(struct module *mod, const Elf_Shdr *sechdrs);
 #else
 static inline int module_finalize_ftrace(struct module *mod, const Elf_Shdr *sechdrs)