Blackfin: fix handling of IPEND in interrupt context save

The interrupt context save logic incorrectly stored the address of the
IPEND register rather than its value due to a missing dereference.  While
we're here, also enable this code for all kernel debugging scenarios and
not just when KGDB is enabled.

Signed-off-by: Robin Getz <robin.getz@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>