crypto/conf: openssl_config_int() returns unitialized value

openssl_config_int() returns the uninitialized variable `ret`
when compiled with OPENSSL_SYS_UEFI.

Fixes #9026

Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/9029)

(cherry picked from commit f4a96507fb880d5f5a707c138388cb8b5b1ba8c8)