[Bug target/86805] sh port needs updating for CVE-2017-5753

[olegendo at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86805

--- Comment #1 from Oleg Endo <olegendo at gcc dot gnu.org> ---
I'm not aware of any SH implementations that do speculative execution or data
access.  So I guess 

#undef TARGET_HAVE_SPECULATION_SAFE_VALUE
#define TARGET_HAVE_SPECULATION_SAFE_VALUE speculation_safe_value_not_needed.

will suffice.