serial: samsung: remove the use of statically remapped controller address

The address S3C_VA_UART is a statically ioremapped address. The driver
should not be using this. Instead, the driver should setup a mapping
during probe.

Cc: Kukjin Kim <kgene.kim@samsung.com>
Signed-off-by: Thomas Abraham <thomas.abraham@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>