crypto: cavium - Fix statistics pending request value

The pending request counter was read from the wrong register. While
at it, there is no need to use an atomic for it as it is only read
localy in a loop.

Signed-off-by: Jan Glauber <jglauber@cavium.com>
Reviewed-by: Robert Richter <rrichter@cavium.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>