crypto: ecc - fix CRYPTO_DEFAULT_RNG dependency

The ecc.c file started out as part of the ECDH algorithm but got
moved out into a standalone module later. It does not build without
CRYPTO_DEFAULT_RNG, so now that other modules are using it as well we
can run into this link error:

aarch64-linux-ld: ecc.c:(.text+0xfc8): undefined reference to `crypto_default_rng'
aarch64-linux-ld: ecc.c:(.text+0xff4): undefined reference to `crypto_put_default_rng'

Move the 'select CRYPTO_DEFAULT_RNG' statement into the correct symbol.

Fixes: 0d7a7864 ("crypto: ecrdsa - add EC-RDSA (GOST 34.10) algorithm")
Fixes: 4e660291 ("crypto: ecdsa - Add support for ECDSA signature verification")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>