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/helios4_defconfig b/configs/helios4_defconfig
index 5a7a60c..62965a4 100644
--- a/configs/helios4_defconfig
+++ b/configs/helios4_defconfig
@@ -43,6 +43,7 @@
 # CONFIG_SPL_PARTITION_UUIDS is not set
 CONFIG_ENV_OVERWRITE=y
 CONFIG_ARP_TIMEOUT=200
+CONFIG_NET_RETRY_COUNT=50
 CONFIG_NET_RANDOM_ETHADDR=y
 CONFIG_SPL_OF_TRANSLATE=y
 CONFIG_AHCI_MVEBU=y