crypto: rng - Mark crypto_rng_reset seed as const

There is no reason why crypto_rng_reset should modify the seed
so this patch marks it as const.  Since our algorithms don't
export a const seed function yet we have to go through some
contortions for now.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --cc crypto/rng.c
Simple merge

diff --cc include/crypto/rng.h
Simple merge