Convert CONFIG_SYS_DEVICE_NULLDEV to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_DEVICE_NULLDEV

Signed-off-by: Simon Glass <sjg@chromium.org>

common/Kconfig

@@ -635,6 +635,22 @@ config SYS_STDIO_DEREGISTER
 	  removed (for example a USB keyboard) then this option can be
 	  enabled to ensure this is handled correctly.
 
+config SPL_SYS_STDIO_DEREGISTER
+	bool "Allow deregistering stdio devices in SPL"
+	help
+	  Generally there is no need to deregister stdio devices since they
+	  are never deactivated. But if a stdio device is used which can be
+	  removed (for example a USB keyboard) then this option can be
+	  enabled to ensure this is handled correctly. This is very rarely
+	  needed in SPL.
+
+config SYS_DEVICE_NULLDEV
+	bool "Enable a null device for stdio"
+	help
+	  Enable creation of a "nulldev" stdio device. This allows silent
+	  operation of the console by setting stdout to "nulldev". Enable
+	  this to use a serial console under board control.
+
 endmenu
 
 menu "Logging"

configs/M5249EVB_defconfig

@@ -5,6 +5,7 @@ CONFIG_ENV_SECT_SIZE=0x2000
 CONFIG_TARGET_M5249EVB=y
 CONFIG_DEFAULT_DEVICE_TREE="M5249EVB"
 CONFIG_SYS_CONSOLE_INFO_QUIET=y
+CONFIG_SYS_DEVICE_NULLDEV=y
 # CONFIG_DISPLAY_BOARDINFO is not set
 # CONFIG_CMDLINE_EDITING is not set
 # CONFIG_AUTOBOOT is not set

configs/colibri_pxa270_defconfig

@@ -10,6 +10,7 @@ CONFIG_ENV_SECT_SIZE=0x40000
 CONFIG_ENV_VARS_UBOOT_CONFIG=y
 CONFIG_USE_BOOTARGS=y
 CONFIG_BOOTARGS="console=tty0 console=ttyS0,115200"
+CONFIG_SYS_DEVICE_NULLDEV=y
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_DISPLAY_BOARDINFO_LATE=y
 # CONFIG_CMDLINE_EDITING is not set

doc/README.silent

@@ -19,7 +19,7 @@ The following actions are taken if "silent" is set at boot time:
  - When the console devices have been initialized, "stdout" and
    "stderr" are set to "nulldev", so subsequent messages are
    suppressed automatically. Make sure to enable "nulldev" by
-   #defining CONFIG_SYS_DEVICE_NULLDEV in your board config file.
+   enabling CONFIG_SYS_DEVICE_NULLDEV in your board defconfig file.
 
  - When booting a linux kernel, the "bootargs" are fixed up so that
    the argument "console=" will be in the command line, no matter how

include/configs/M5249EVB.h

@@ -31,8 +31,6 @@
  */
 #undef CONFIG_BOOTP_BOOTFILESIZE
 
-#define CONFIG_SYS_DEVICE_NULLDEV	1	/* include nulldev device	*/
-
 #define CONFIG_SYS_LOAD_ADDR		0x200000	/* default load address */
 
 /*

include/configs/colibri_pxa270.h

@@ -69,8 +69,6 @@
 #define	CONFIG_BOOTP_BOOTFILESIZE
 #endif
 
-#define	CONFIG_SYS_DEVICE_NULLDEV	1
-
 /*
  * Clock Configuration
  */

scripts/config_whitelist.txt

@@ -2117,7 +2117,6 @@ CONFIG_SYS_DEBUG_SERVER_FW_IN_NOR
 CONFIG_SYS_DEFAULT_LPDDR2_TIMINGS
 CONFIG_SYS_DEFAULT_VIDEO_MODE
 CONFIG_SYS_DEF_EEPROM_ADDR
-CONFIG_SYS_DEVICE_NULLDEV
 CONFIG_SYS_DFU_DATA_BUF_SIZE
 CONFIG_SYS_DFU_MAX_FILE_SIZE
 CONFIG_SYS_DIAG_ADDR