crypto: skcipher - unify the crypto_has_skcipher*() functions

crypto_has_skcipher() and crypto_has_skcipher2() do the same thing: they
check for the availability of an algorithm of type skcipher, blkcipher,
or ablkcipher, which also meets any non-type constraints the caller
specified.  And they have exactly the same prototype.

Therefore, eliminate the redundancy by removing crypto_has_skcipher()
and renaming crypto_has_skcipher2() to crypto_has_skcipher().

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>