serial: samsung: enable clock before clearing pending interrupts during init

Ensure that the uart controller clock is enabled prior to writing to the
interrupt mask and pending registers in the s3c24xx_serial_init_port
function.

Signed-off-by: Chander Kashyap <chander.kashyap@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>