Convert CONFIG_SYS_FLASH_EMPTY_INFO to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_FLASH_EMPTY_INFO

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/mccmon6_sd_defconfig b/configs/mccmon6_sd_defconfig
index 6984256..111c0f0 100644
--- a/configs/mccmon6_sd_defconfig
+++ b/configs/mccmon6_sd_defconfig
@@ -61,6 +61,7 @@
 CONFIG_FLASH_CFI_DRIVER=y
 CONFIG_SYS_FLASH_CFI_WIDTH_16BIT=y
 CONFIG_SYS_FLASH_USE_BUFFER_WRITE=y
+CONFIG_SYS_FLASH_EMPTY_INFO=y
 CONFIG_FLASH_CFI_MTD=y
 CONFIG_SYS_FLASH_PROTECTION=y
 CONFIG_SYS_FLASH_CFI=y