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/kp_imx53_defconfig b/configs/kp_imx53_defconfig
index d2e09ac..3ec3347 100644
--- a/configs/kp_imx53_defconfig
+++ b/configs/kp_imx53_defconfig
@@ -39,6 +39,7 @@
 CONFIG_ENV_IS_IN_MMC=y
 CONFIG_SYS_REDUNDAND_ENVIRONMENT=y
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y
+CONFIG_ARP_TIMEOUT=200
 CONFIG_I2C_SET_DEFAULT_BUS_NUM=y
 CONFIG_I2C_DEFAULT_BUS_NUMBER=0x1
 CONFIG_SYS_I2C_MXC=y