[CRYPTO] geode: relax in busy loop and care about return value

The code waits in a busy loop until the hardware finishes the encryption
or decryption process. This wants a cpu_relax() :)
The busy loop finishes either if the encryption is done or if the counter
is zero. If the latter is true than the hardware failed. Since this
should not happen, leave sith a BUG().

Signed-off-by: Sebastian Siewior <sebastian@breakpoint.cc>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>