crypto: stm32 - remove flag HASH_FLAGS_DMA_READY

Remove flag HASH_FLAGS_DMA_READY as it can put the driver in a deadlock
state.
If the DMA automatically set the DCAL bit, the interrupt indicating the
end of a computation can be raised before the DMA complete sequence.

Signed-off-by: Thomas Bourgoin <thomas.bourgoin@foss.st.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>