s390/fgraph: Fix to remove ftrace_test_recursion_trylock()

Fix to remove ftrace_test_recursion_trylock() from ftrace_graph_func()
because commit d576aec2 ("fgraph: Get ftrace recursion lock in
function_graph_enter") has been moved it to function_graph_enter_regs()
already.

Reported-by: Jiri Olsa <olsajiri@gmail.com>
Closes: https://lore.kernel.org/all/Z5O0shrdgeExZ2kF@krava/


Fixes: d576aec2 ("fgraph: Get ftrace recursion lock in function_graph_enter")
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Tested-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Ihor Solodrai <ihor.solodrai@linux.dev>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Link: https://lore.kernel.org/r/173807817692.1854334.2985776940754607459.stgit@devnote2


Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>