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/mvebu_crb_cn9130_defconfig b/configs/mvebu_crb_cn9130_defconfig
index 62aeafc..ceb53c7 100644
--- a/configs/mvebu_crb_cn9130_defconfig
+++ b/configs/mvebu_crb_cn9130_defconfig
@@ -42,6 +42,7 @@
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y
 CONFIG_SYS_MMC_ENV_DEV=1
 CONFIG_ARP_TIMEOUT=200
+CONFIG_NET_RETRY_COUNT=50
 CONFIG_AHCI_MVEBU=y
 CONFIG_DM_I2C=y
 CONFIG_SYS_I2C_MVTWSI=y