crypto: jitterentropy - always select CRYPTO_RNG

When building the jitterentropy driver by itself, we get a link error
when CRYPTO_RNG is not enabled as well:

crypto/built-in.o: In function `jent_mod_init':
jitterentropy-kcapi.c:(.init.text+0x98): undefined reference to `crypto_register_rng'
crypto/built-in.o: In function `jent_mod_exit':
jitterentropy-kcapi.c:(.exit.text+0x60): undefined reference to `crypto_unregister_rng'

This adds a 'select CRYPTO_RNG' to CRYPTO_JITTERENTROPY to ensure the API
is always there when it's used, not just when DRBG is also enabled.
CRYPTO_DRBG would set it implicitly through CRYPTO_JITTERENTROPY now,
but this leaves it in place to make it explicit what the driver does.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/Kconfig

@@ -1574,6 +1574,7 @@ endif	# if CRYPTO_DRBG_MENU
 
 config CRYPTO_JITTERENTROPY
 	tristate "Jitterentropy Non-Deterministic Random Number Generator"
+	select CRYPTO_RNG
 	help
 	  The Jitterentropy RNG is a noise that is intended
 	  to provide seed to another RNG. The RNG does not