hwrng: cctrng - change default to n

For many users, the Arm CryptoCell HW is not available, so the default for
HW_RANDOM_CCTRNG should to n.
Remove the line to follow the convention - 'n' is the default anyway so no
need to state it explicitly.

Signed-off-by: Hadar Gat <hadar.gat@arm.com>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>