powerpc/ftrace: add ftrace.h, fix sparse warning

[Michael Ellerman]

On Mon, 2017-03-06 at 08:49:46 UTC, "Tobin C. Harding" wrote:
> Sparse emits warning: symbol 'prepare_ftrace_return' was not
> declared. Should it be static? prepare_ftrace_return() is called
> from assembler and should not be static. Adding a header file
> declaring the function will fix the sparse warning while adding
> documentation to the call.
> 
> Add header file ftrace.h with single function declaration. Protect
> declaration with preprocessor guard so it may be included in
> assembly. Include new header in all files that call
> prepare_ftrace_return() and in ftrace.c where function is defined.
> 
> Signed-off-by: Tobin C. Harding <me at tobin.cc>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/b3a7864c6feb0fb30bc2cd37265707

cheers