Convert CONFIG_BOOTP_MAY_FAIL et al to Kconfig

This converts the following to Kconfig:
   CONFIG_BOOTP_MAY_FAIL
   CONFIG_BOOTP_VENDOREX
   CONFIG_BOOTP_BOOTFILESIZE
   CONFIG_BOOTP_NISDOMAIN
   CONFIG_BOOTP_TIMEOFFSET

Cc: Ramon Fried <rfried.dev@gmail.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/syzygy_hub_defconfig b/configs/syzygy_hub_defconfig
index 6dbf8c2..cbc6208 100644
--- a/configs/syzygy_hub_defconfig
+++ b/configs/syzygy_hub_defconfig
@@ -37,6 +37,7 @@
 CONFIG_CMD_MMC=y
 CONFIG_CMD_USB=y
 # CONFIG_CMD_SETEXPR is not set
+CONFIG_BOOTP_MAY_FAIL=y
 CONFIG_CMD_TFTPPUT=y
 CONFIG_CMD_CACHE=y
 CONFIG_CMD_EXT4_WRITE=y