ssl.c: use arrow operator to access object member

ssl.c: use arrow operator to access object member

The arrow operator exists exactly to perform a pointer dereference
implicitly
while accessing a member.

while at it, add whitespaces around the '-' operator on the same line.

Signed-off-by: Antonio Quartulli <a@unstable.cc>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20220110144510.17769-1-a@unstable.cc>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg23521.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>