linux-wandboard

sh: ftrace: Make code modification NMI safe.

This cribs the x86 implementation of ftrace_nmi_enter() and friends to
make ftrace_modify_code() NMI safe, particularly on SMP configurations.

For additional notes on the problems involved, see the comment below
ftrace_call_replace().

Signed-off-by: Paul Mundt <lethal@linux-sh.org>