serial: Convert ARC_SERIAL to Kconfig

One step closer to completely Kconfig-driven target configuration in
U-Boot :)

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>

configs/nsim_700_defconfig

@@ -13,4 +13,5 @@ CONFIG_OF_CONTROL=y
 CONFIG_OF_EMBED=y
 CONFIG_DM=y
 CONFIG_DM_SERIAL=y
+CONFIG_ARC_SERIAL=y
 CONFIG_USE_PRIVATE_LIBGCC=y

configs/nsim_700be_defconfig

@@ -14,4 +14,5 @@ CONFIG_OF_CONTROL=y
 CONFIG_OF_EMBED=y
 CONFIG_DM=y
 CONFIG_DM_SERIAL=y
+CONFIG_ARC_SERIAL=y
 CONFIG_USE_PRIVATE_LIBGCC=y

configs/nsim_hs38_defconfig

@@ -14,4 +14,5 @@ CONFIG_OF_CONTROL=y
 CONFIG_OF_EMBED=y
 CONFIG_DM=y
 CONFIG_DM_SERIAL=y
+CONFIG_ARC_SERIAL=y
 CONFIG_USE_PRIVATE_LIBGCC=y

configs/nsim_hs38be_defconfig

@@ -15,4 +15,5 @@ CONFIG_OF_CONTROL=y
 CONFIG_OF_EMBED=y
 CONFIG_DM=y
 CONFIG_DM_SERIAL=y
+CONFIG_ARC_SERIAL=y
 CONFIG_USE_PRIVATE_LIBGCC=y

drivers/serial/Kconfig

@@ -425,6 +425,13 @@ config AR933X_UART
 	  tree binding to operate, please refer to the document at
 	  doc/device-tree-bindings/serial/qca,ar9330-uart.txt.
 
+config ARC_SERIAL
+	bool "ARC UART support"
+	depends on DM_SERIAL
+	help
+	  Select this to enable support for ARC UART now typically
+	  only used in Synopsys DesignWare ARC simulators like nSIM.
+
 config ATMEL_USART
 	bool "Atmel USART support"
 	help

include/configs/nsim.h

@@ -24,16 +24,6 @@
 #define CONFIG_SYS_BOOTM_LEN		SZ_32M
 #define CONFIG_SYS_LOAD_ADDR		0x82000000
 
-/*
- * UART configuration
- *
- */
-#define CONFIG_ARC_SERIAL
-
-/*
- * Command line configuration
- */
-
 /*
  * Environment settings
  */

scripts/config_whitelist.txt

@@ -47,7 +47,6 @@ CONFIG_ARCH_RMOBILE_EXTRAM_BOOT
 CONFIG_ARCH_TEGRA
 CONFIG_ARCH_USE_BUILTIN_BSWAP
 CONFIG_ARC_MMU_VER
-CONFIG_ARC_SERIAL
 CONFIG_ARIES_M28_V10
 CONFIG_ARMADA100
 CONFIG_ARMADA100_FEC