hwrng: ingenic - don't disable the rng in ingenic_trng_remove

There's no need to disable the rng in ingenic_trng_remove.

The driver's init function sets the CFG_GEN_EN bit to enable the
rng. The cleanup function clears CFG_GEN_EN to revert this.

The remove function calls hwrng_unregister. If the ingenic-trng is not
the current rng at this point, CFG_GEN_EN has already been cleared. If
the ingenic-trng is the current rng, drop_current_rng will call the
cleanup function.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>