crypto: talitos - handle descriptor not found in error path

The CDPR (Current Descriptor Pointer Register) can be unreliable
when trying to locate an offending descriptor.  Handle that case by
(a) not OOPSing, and (b) reverting to the machine internal copy of
the descriptor header in order to report the correct execution unit
error.

Note: printing all execution units' ISRs is not effective because it
results in an internal time out (ITO) error and the EU resetting its
ISR value (at least when specifying an invalid key length on an SEC
2.2/MPC8313E).

Reported-by: Sven Schnelle <svens@stackframe.org>
Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>