crypto/bio/bio_print.c: avoid signed int overflow in desc->pos in doapr_outch

crypto/bio/bio_print.c: avoid signed int overflow in desc->pos in doapr_outch

While highly improbable, a signed integer overflow can be triggered
by incrementing desc->pos LLONG_MAX + 1 times.

Fixes: 228ef5f54727 "crypto/bio/bio_print.c: make %n in line with other libc implementations"
Signed-off-by: Eugene Syromiatnikov <esyr@openssl.org>
Reviewed-by: Neil Horman <nhorman@openssl.org>
Reviewed-by: Saša Nedvědický <sashan@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/28502)