wireguard: Kconfig: select parent dependency for crypto

This fixes the crypto selection submenu depenencies. Otherwise, we'd
wind up issuing warnings in which certain dependencies we also select
couldn't be satisfied. This condition was triggered by the addition of
the test suite autobuilder in the previous commit.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: David S. Miller <davem@davemloft.net>