crypto: stm32/crc32 - fix multi-instance

Ensure CRC algorithm is registered only once in crypto framework when
there are several instances of CRC devices.

Update the CRC device list management to avoid that only the first CRC
instance is used.

Fixes: b51dbe90 ("crypto: stm32 - Support for STM32 CRC32 crypto module")

Signed-off-by: Nicolas Toromanoff <nicolas.toromanoff@st.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>