Convert CONFIG_BOOTP_DNS2 to Kconfig

This converts the following to Kconfig:
   CONFIG_BOOTP_DNS2
   CONFIG_BOOTP_PXE_CLIENTARCH

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/da850evm_nand_defconfig b/configs/da850evm_nand_defconfig
index 179a178..9610364 100644
--- a/configs/da850evm_nand_defconfig
+++ b/configs/da850evm_nand_defconfig
@@ -33,6 +33,7 @@
 # CONFIG_CMD_GPT is not set
 CONFIG_CMD_NAND=y
 # CONFIG_CMD_SETEXPR is not set
+CONFIG_BOOTP_DNS2=y
 # CONFIG_CMD_TIME is not set
 # CONFIG_CMD_EXT4 is not set
 CONFIG_CMD_MTDPARTS=y