hwrng: remove Michael as HWRNG maintainer

It turns out that I rewrote the HWRNG core once to make it pluggable, but
I'm not a crypto-expert at all.  So I'm certainly the wrong person for
being a maintainer of the HWRNG core.  Let's orphan it.

Signed-off-by: Michael Buesch <mb@bu3sch.de>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>