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/am43xx_evm_qspiboot_defconfig b/configs/am43xx_evm_qspiboot_defconfig
index 39facf1..459096d 100644
--- a/configs/am43xx_evm_qspiboot_defconfig
+++ b/configs/am43xx_evm_qspiboot_defconfig
@@ -26,6 +26,7 @@
 CONFIG_CMD_SPI=y
 CONFIG_CMD_USB=y
 # CONFIG_CMD_SETEXPR is not set
+CONFIG_BOOTP_DNS2=y
 CONFIG_CMD_EXT4_WRITE=y
 CONFIG_OF_CONTROL=y
 CONFIG_DEFAULT_DEVICE_TREE="am437x-sk-evm"