crypto: ecc - Add NIST P521 curve parameters

Add the parameters for the NIST P521 curve and define a new curve ID
for it. Make the curve available in ecc_get_curve.

Tested-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>