crypto: ecc - Add NIST P384 curve parameters

Add the parameters for the NIST P384 curve and define a new curve ID
for it. Make the curve available in ecc_get_curve.

Summary of changes:

* crypto/ecc_curve_defs.h
  - add nist_p384 params

* include/crypto/ecdh.h
  - add ECC_CURVE_NIST_P384

* crypto/ecc.c
  - change ecc_get_curve to accept nist_p384

Signed-off-by: Saulo Alessandre <saulo.alessandre@tse.jus.br>
Tested-by: Stefan Berger <stefanb@linux.ibm.com>
Acked-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>