tracing, powerpc: fix powerpc tree and tracing tree interaction

Today's linux-next build (powerpc allyesconfig) failed like this:

arch/powerpc/kernel/ftrace.c: In function 'prepare_ftrace_return':
arch/powerpc/kernel/ftrace.c:612: warning: passing argument 3 of 'ftrace_push_return_trace' makes pointer from integer without a cast
arch/powerpc/kernel/ftrace.c:612: error: too many arguments to function 'ftrace_push_return_trace'

Caused by commit 5d1a03dc
("function-graph: moved the timestamp from arch to generic code") from
the tracing tree which (removed an argument from
ftrace_push_return_trace()) interacting with commit
6794c782

 ("powerpc64: port of the
function graph tracer") from the powerpc tree.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Steven Rostedt <srostedt@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: <linuxppc-dev@ozlabs.org>
LKML-Reference: <20090327230834.93d0221d.sfr@canb.auug.org.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>