Convert CONFIG_NET_RETRY_COUNT to Kconfig

This converts the following to Kconfig:
   CONFIG_NET_RETRY_COUNT

Cc: Ramon Fried <rfried.dev@gmail.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/colibri_pxa270_defconfig b/configs/colibri_pxa270_defconfig
index a955ba5..e8ebe85 100644
--- a/configs/colibri_pxa270_defconfig
+++ b/configs/colibri_pxa270_defconfig
@@ -39,6 +39,7 @@
 CONFIG_ENV_IS_IN_FLASH=y
 CONFIG_ENV_ADDR=0x80000
 CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG=y
+CONFIG_NET_RETRY_COUNT=10
 CONFIG_DM=y
 CONFIG_PXA_MMC_GENERIC=y
 CONFIG_MTD_NOR_FLASH=y