Blackfin: workaround anomaly 05000310

While fetching instructions at the boundary of L1 instruction SRAM, a false
External Memory Addressing Error might be triggered.  We should ignore this
and continue on our way to avoid random crashes.

Because hardware errors are not exact in the Blackfin architecture, we need
to catch a few more common cases when the code flow changes and the signal
is finally delivered.

Signed-off-by: Barry Song <barry.song@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>