crypto: sun4i-ss - Remove insecure and unused rng_alg

Summary

In the Linux kernel, the following vulnerability has been resolved: crypto: sun4i-ss - Remove insecure and unused rng_alg Remove sun4i_ss_rng, as it is insecure and unused: - It has multiple vulnerabilities. sun4i_ss_prng_seed() is missing locking and has a buffer overflow. sun4i_ss_prng_generate() fails to fill the entire buffer with cryptographic random bytes, because it rounds the destination length down and also doesn't actually wait for the hardware to be ready before pulling bytes from it. - No user of this code is known. It's usable only theoretically via the "rng" algorithm type of AF_ALG. But userspace actually just uses the actual Linux RNG (/dev/random etc) instead. And rng_algs don't contribute entropy to the actual Linux RNG either. (This may have been confused with hwrng, which does contribute entropy.) The sun4i_ss_prng_seed() buffer overflow was reported by Tianchu Chen and discovered by Atuin - Automated Vulnerability Discovery Engine There's no point in fixing all these vulnerabilities individually when this is unused code, so let's just remove it.