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/apf27_defconfig b/configs/apf27_defconfig
index 73a5304..88f1b54 100644
--- a/configs/apf27_defconfig
+++ b/configs/apf27_defconfig
@@ -29,6 +29,7 @@
 CONFIG_CMD_NAND_TRIMFFS=y
 CONFIG_CMD_NAND_LOCK_UNLOCK=y
 CONFIG_CMD_DHCP=y
+CONFIG_BOOTP_DNS2=y
 CONFIG_CMD_MII=y
 CONFIG_CMD_PING=y
 CONFIG_CMD_DNS=y