sh/ftrace: Remove only user of ftrace_arch_read_dyn_info()

sh/ftrace: Remove only user of ftrace_arch_read_dyn_info()

I noticed that there's only one user of ftrace_arch_read_dyn_info().
That was used a while ago during the NMI updating in x86, and superh
copied it to implement its version of handling NMIs during
stop_machine().

But that is a debug feature, and this code hasn't been touched since
2009. Also, x86 no longer does the ftrace updates with stop_machine()
and instead uses breakpoints. If superh needs to modify its code, it
should implement the breakpoint conversion, and remove stop_machine().
Which also gets rid of the NMI issue.

Anyway, I want to nuke ftrace_arch_read_dyn_info() and this gets rid of
the one user, which is for an arch that shouldn't need it anymore.

Link: http://lkml.kernel.org/r/20170626181749.2ce954d1@gandalf.local.home
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Cc: linux-sh@vger.kernel.org
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>