toolchain: m68k coldfire is also affected by gcc bug 64735

Verified experimentally by using exception_ptr with m68k_cf5208 and
looking at the value of ATOMIC_INT_LOCK_FREE. ATOMIC_INT_LOCK_FREE=1,
so the issue is present. Also verified that gcc 7.x fixed it also for
cf5208.

Signed-off-by: Jan Heylen <jan.heylen@nokia.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>