Convert CONFIG_UDP_CHECKSUM to Kconfig

This converts the following to Kconfig:
   CONFIG_UDP_CHECKSUM

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/M53017EVB_defconfig b/configs/M53017EVB_defconfig
index 1cd48d6..b8292fd 100644
--- a/configs/M53017EVB_defconfig
+++ b/configs/M53017EVB_defconfig
@@ -21,6 +21,7 @@
 CONFIG_CMD_DATE=y
 CONFIG_ENV_IS_IN_FLASH=y
 CONFIG_ENV_ADDR=0x40000
+CONFIG_UDP_CHECKSUM=y
 CONFIG_SYS_I2C_LEGACY=y
 CONFIG_SYS_I2C_FSL=y
 CONFIG_SYS_FSL_I2C_OFFSET=0x58000