crypto: rng - Don't pull in DRBG when CRYPTO_FIPS=n

crypto: rng - Don't pull in DRBG when CRYPTO_FIPS=n

crypto_stdrng_get_bytes() is now always available:

    - When CRYPTO_FIPS=n it is an inline function that always calls into
      the always-built-in drivers/char/random.c.

    - When CRYPTO_FIPS=y it is an inline function that calls into either
      random.c or crypto/rng.c, depending on the value of fips_enabled.
      The former is again always built-in.  The latter is built-in as
      well in this case, due to CRYPTO_FIPS=y.

Thus, the CRYPTO_RNG_DEFAULT symbol is no longer needed.  Remove it.

This makes it so that CRYPTO_DRBG_MENU (and hence also CRYPTO_DRBG,
CRYPTO_JITTERENTROPY, and CRYPTO_LIB_SHA3) no longer gets unnecessarily
pulled into CRYPTO_FIPS=n kernels.  I.e. CRYPTO_FIPS=n kernels are no
longer bloated with code that is relevant only to FIPS certifications.

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