Convert CONFIG_ARP_TIMEOUT to Kconfig

This converts the following to Kconfig:
   CONFIG_ARP_TIMEOUT

Cc: Ramon Fried <rfried.dev@gmail.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/imx6q_logic_defconfig b/configs/imx6q_logic_defconfig
index bd5853c..94e8bd0 100644
--- a/configs/imx6q_logic_defconfig
+++ b/configs/imx6q_logic_defconfig
@@ -69,6 +69,7 @@
 CONFIG_ENV_FAT_DEVICE_AND_PART="0:1"
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y
 CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG=y
+CONFIG_ARP_TIMEOUT=200
 CONFIG_SPL_DM=y
 CONFIG_SPL_DM_SEQ_ALIAS=y
 CONFIG_SPL_OF_TRANSLATE=y