Assume TERMIOS is default, remove TERMIO on all Linux.

The rationale for this move is that TERMIOS is default, supported by
POSIX-1.2001, and most definitely on Linux.  For a few other systems,
TERMIO may still be the termnial interface of preference, so we keep
-DTERMIO on those in Configure.

crypto/ui/ui_openssl.c is simplified in this regard, and will define
TERMIOS for all systems except a select few exceptions.
Reviewed-by: Matt Caswell <matt@openssl.org>