crypto: xilinx-trng - Remove crypto_rng interface

In the Linux kernel, the following vulnerability has been resolved: 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.