sm: Support import of PKCS#12 encoded ECC private keys.
* sm/import.c (parse_p12): Support ECC import.
Although I extended the parser and its test the actual import
missed the required code.
Backported-from-master: 8dfef5197af9f655697e0095c6613137d51c91e7
- GnuPG-bug-id: T6253