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/kmnusa_defconfig b/configs/kmnusa_defconfig
index d81c787..b8433b7 100644
--- a/configs/kmnusa_defconfig
+++ b/configs/kmnusa_defconfig
@@ -37,6 +37,7 @@
 # CONFIG_CMD_FLASH is not set
 CONFIG_CMD_I2C=y
 CONFIG_CMD_NAND=y
+CONFIG_BOOTP_BOOTFILESIZE=y
 CONFIG_CMD_MII=y
 CONFIG_CMD_PING=y
 CONFIG_CMD_MTDPARTS=y