crypto: xilinx-trng - Remove crypto_rng interface

crypto: xilinx-trng - Remove crypto_rng interface

Implementing the crypto_rng interface has no purpose, as it isn't used
in practice.  It's being removed from other drivers too.  Just remove
it.  This leaves hwrng, which is actually used.

Tagging with 'Cc stable' due to the bugs that this removes:

  - xtrng_trng_generate() sometimes returned success even when it didn't
    fill in all the bytes.

  - It was possible for xtrng_trng_generate() and
    xtrng_hwrng_trng_read() to run concurrently and interfere with each
    other, as the locking code in xtrng_hwrng_trng_read() was broken.

Fixes: 8979744aca80 ("crypto: xilinx - Add TRNG driver for Versal")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>