crypto: drbg - Remove always-enabled symbol CRYPTO_DRBG_HMAC

crypto: drbg - Remove always-enabled symbol CRYPTO_DRBG_HMAC

The kconfig symbol CRYPTO_DRBG_HMAC is always enabled when
CRYPTO_DRBG_MENU is enabled, and all checks for CRYPTO_DRBG_HMAC are in
code conditional on CRYPTO_DRBG_MENU.  Thus, the only purpose of the
CRYPTO_DRBG_HMAC symbol is to select CRYPTO_HMAC and CRYPTO_SHA512.

Move those two selections to CRYPTO_DRBG_MENU, remove the checks for
CRYPTO_DRBG_HMAC, and remove the CRYPTO_DRBG_HMAC symbol itself.

Note that this also fixes an issue where CRYPTO_HMAC and CRYPTO_SHA512
were unnecessarily being forced to built-in when CRYPTO_DRBG=m.

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