serial: mcf: add sysrq capability

After some unsuccessful attempts to use sysrq over console, figured
out that port->has_sysrq should likely be enabled, as per other
architectures, this when CONFIG_SERIAL_MCF_CONSOLE is also enabled.

Tested some magic sysrq commands (h, p, t, b), they works now
properly. Commands works inside 5 secs after BREAK is sent, as
expected.

Signed-off-by: Angelo Dureghello <angelo.dureghello@timesys.com>
Link: https://lore.kernel.org/r/20201002140545.477481-1-angelo.dureghello@timesys.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>