tty: serial: samsung: constify s3c24xx_serial_drv_data members

tty: serial: samsung: constify s3c24xx_serial_drv_data members

The driver data (struct s3c24xx_serial_drv_data) is never modified, so
also its members can be made const.  Except code style this has no
impact because the structure itself is always a const.

Tested-by: Alim Akhtar <alim.akhtar@samsung.com>
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20220308080919.152715-7-krzysztof.kozlowski@canonical.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>