serial: 8250: Only get RSA resource when required

The probe for Remote Supervisor Adapter is limited to port i/o
addresses which match one of the probe_rsa[] module parameter
addresses. Limit RSA resource acquire to matching i/o ports.

The result is a saner probe policy: only perform optional probes
when specified rather than by default.

NB: It is possible for userspace to set the port type == PORT_RSA
with ioctl(TIOCSSERIAL) and then autoconfig with ioctl(TIOCSERCONFIG),
which if it fails, may leave the port type set to PORT_RSA. Since
this may have previously resulted in a working RSA port, this behavior
is preserved.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>