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/cobra5272_defconfig b/configs/cobra5272_defconfig
index 4fc3b0a..ce1c4e0 100644
--- a/configs/cobra5272_defconfig
+++ b/configs/cobra5272_defconfig
@@ -15,6 +15,7 @@
 # CONFIG_CMD_LOADB is not set
 # CONFIG_CMD_LOADS is not set
 # CONFIG_CMD_SETEXPR is not set
+CONFIG_BOOTP_BOOTFILESIZE=y
 CONFIG_CMD_PING=y
 CONFIG_ENV_ADDR=0xFFE04000
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y