board: sl28: enable DM_SERIAL

With all preparations in place, switch over to DM_SERIAL.

Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>

arch/arm/Kconfig

@@ -1616,6 +1616,7 @@ config TARGET_SL28
 	select DM_RNG
 	select DM_RTC
 	select DM_SCSI
+	select DM_SERIAL
 	select DM_SPI
 	select DM_USB
 	select SPL_DM if SPL

include/configs/kontron_sl28.h

@@ -49,8 +49,6 @@
 #define CONFIG_MALLOC_F_ADDR		CONFIG_SYS_FSL_OCRAM_BASE
 
 /* serial port */
-#define CONFIG_SYS_NS16550_SERIAL
-#define CONFIG_SYS_NS16550_REG_SIZE 1
 #define CONFIG_SYS_NS16550_CLK          (get_bus_freq(0) / 2)
 #define CONFIG_SYS_BAUDRATE_TABLE	{ 9600, 19200, 38400, 57600, 115200 }