serial: bfin_5xx: IRDA is not affected by anomaly 05000230

Anomaly 05000230 (over sampling of the UART STOP bit) applies only when
the peripheral is operating in UART mode.  So drop the anomaly handling
when the UART is in IRDA mode.

Signed-off-by: Graf Yang <graf.yang@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>