serial: omap-serial: Enable the UART wake-up bits always

OMAP can do also dynamic idling so wake-up enable register should be set
also while system is running. If UART_OMAP_WER is not set, then for instance
the RX activity cannot wake up the UART port that is sleeping.

This RX wake-up feature was working when the 8250 driver was used instead
of omap-serial. Reason for this is that the 8250 doesn't set the
UART_OMAP_WER and then arch/arm/mach-omap2/pm34xx.c ends up saving and
restoring the reset default which is the same than value
OMAP_UART_WER_MOD_WKUP here.

Fix this by moving the conditional UART_OMAP_WER write from serial_omap_pm
into serial_omap_startup where wake-up bits are set unconditionally.

Signed-off-by: Jarkko Nikula <jhnikula@gmail.com>
Cc: Govindraj.R <govindraj.raja@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>