board: Enable ethernet, tftpboot support to pic32mzdask board.

This adds ethernet, TFTP support for PIC32MZ[DA] Starter Kit. Also
custom environment variables/scripts are added to help boot from network.

Signed-off-by: Purna Chandra Mandal <purna.mandal@microchip.com>
diff --git a/configs/pic32mzdask_defconfig b/configs/pic32mzdask_defconfig
index 55ba3f8..169a2ac 100644
--- a/configs/pic32mzdask_defconfig
+++ b/configs/pic32mzdask_defconfig
@@ -16,16 +16,19 @@
 # CONFIG_CMD_FLASH is not set
 # CONFIG_CMD_FPGA is not set
 CONFIG_CMD_GPIO=y
-# CONFIG_CMD_NET is not set
-# CONFIG_CMD_NFS is not set
+CONFIG_CMD_RARP=y
+CONFIG_CMD_DHCP=y
+CONFIG_CMD_PING=y
 CONFIG_CMD_TIME=y
 CONFIG_OF_EMBED=y
+CONFIG_NET_RANDOM_ETHADDR=y
 CONFIG_CLK=y
 CONFIG_DM_MMC=y
 CONFIG_PIC32_SDHCI=y
+CONFIG_DM_ETH=y
+CONFIG_PIC32_ETH=y
 CONFIG_PINCTRL=y
 # CONFIG_PINCTRL_FULL is not set
 CONFIG_SYS_VSNPRINTF=y
 CONFIG_USE_TINY_PRINTF=y
-CONFIG_REGEX=y
 CONFIG_CMD_DHRYSTONE=y