hwrng: Kconfig - Use tabs as leading whitespace consistently in Kconfig

Replace instances of leading size-eight groups of space characters with
the usual tab characters, as spotted in the hw_random Kconfig file.

No intended functional changes are introduced by this trivial cleanup.

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