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/pic32mzdask_defconfig b/configs/pic32mzdask_defconfig
index 6380725..d5008c4 100644
--- a/configs/pic32mzdask_defconfig
+++ b/configs/pic32mzdask_defconfig
@@ -32,6 +32,7 @@
 # CONFIG_EFI_PARTITION is not set
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y
 CONFIG_ARP_TIMEOUT=500
+CONFIG_NET_RETRY_COUNT=20
 CONFIG_NET_RANDOM_ETHADDR=y
 CONFIG_CLK=y
 CONFIG_MMC=y