Blackfin arch: fix bug cplbmgr.S does not exit properly on error condition

https://blackfin.uclinux.org/gf/project/uclinux-dist/tracker/?action=TrackerItemEdit&tracker_item_id=1685

Ensure that cache/protection is turned back on when we get a
fault, and ensure that the initial population of the CPLB tables are
correct - that kernel is locked in CPLB tables

Signed-off-by: Robin Getz <robin.getz@analog.com>
Signed-off-by: Bryan Wu <bryan.wu@analog.com>