crypto: omap-sham - replace flags bit mask with bit number

Flags mask cannot be used with atomic bit operations.
This patch changes masks to bit numbers.
Atomic bit operations will be used by following patches.

Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@nokia.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>