Convert CONFIG_DOS_PARTITION to Kconfig

This converts the following to Kconfig:
   CONFIG_DOS_PARTITION

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/SBx81LIFKW_defconfig b/configs/SBx81LIFKW_defconfig
index b0903d6..1669016 100644
--- a/configs/SBx81LIFKW_defconfig
+++ b/configs/SBx81LIFKW_defconfig
@@ -26,6 +26,7 @@
 CONFIG_CMD_MII=y
 CONFIG_CMD_PING=y
 CONFIG_CMD_SNTP=y
+CONFIG_DOS_PARTITION=y
 CONFIG_OF_CONTROL=y
 CONFIG_ENV_OVERWRITE=y
 CONFIG_ENV_IS_IN_SPI_FLASH=y