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/ds414_defconfig b/configs/ds414_defconfig
index fad924d..41fa2cd 100644
--- a/configs/ds414_defconfig
+++ b/configs/ds414_defconfig
@@ -54,6 +54,7 @@
 CONFIG_ENV_SPI_MAX_HZ=50000000
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y
 CONFIG_ARP_TIMEOUT=200
+CONFIG_NET_RETRY_COUNT=50
 CONFIG_SPL_OF_TRANSLATE=y
 CONFIG_DM_I2C=y
 CONFIG_SYS_I2C_MVTWSI=y