crypto: stm32/hash - Fix hmac issue more than 256 bytes

commit 0acabecebc912b3ba06289e4ef40476acc499a37 upstream.

Correct condition for the second hmac loop. Key must be only
set in the first loop. Initial condition was wrong,
HMAC_KEY flag was not properly checked.

Signed-off-by: Lionel Debieve <lionel.debieve@st.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>