ecc: ECDSA adjustments for FIPS 186-4

* cipher/ecc-curves.c: Unmark curve P-192 for FIPS.
* cipher/ecc.c: Add ECDSA self test.
* cipher/pubkey-util.c (_gcry_pk_util_init_encoding_ctx): Use SHA-2
in FIPS mode.
* tests/fipsdrv.c: Add support for ECDSA signatures.

Enable ECC in FIPS mode.
According to NIST SP 800-131A, curve P-192 and SHA-1 are disallowed
for key pair generation and signature generation after 2013.

Thanks to Jan Matejek for the patch.

Minor source code re-formatting by -wk.

• Signed-off-by: Vitezslav Cizek <vcizek@suse.com>