Disable the EGD seeding meachanism when stdio is disabled

crypto/rand/rand_egd.c makes extensive use of stdio functions.  When
they are disabled, it makes sense to disable egd as well.

Reviewed-by: Tim Hudson <tjh@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4358)

(cherry picked from commit 15a1bd0a)