No RDRAND online health tests (NIST SP 800-90B repetition / adaptive-proportion)

Summary

rdrand_rng_harvest feeds RDRAND output directly into CSPRNG pool with no per-source health checks (no repetition-count test no adaptive-proportion test no startup/self-test). NIST SP 800-90B requires these noise-source health tests. Driver relies entirely on downstream L15/IBAA/csprng mixing for safety. rdrand_rng assembly performs no retry budget single CF=0 immediately terminates read so flaky RDRAND silently yields fewer bytes. In virtualized environment hostile hypervisor can intercept RDRAND return biased/attacker-chosen values with no health test driver has no way to detect. Design observation not demonstrable exploit.