Fix an integer overflow in o_time.c

Fix an integer overflow in o_time.c

If input offset_sec is sufficiently large (> INT32_MAX * SECS_PER_DAY, which is possible for a long on 64-bit platforms), then the first assignment contains an overflow.

I think leaving offset_hms as an int is still safe.

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/14252)