bootloader for as204te, use kexec to boot another kernel from CEFDK.

Usage
------
```bash
# make kbl_defconfig
# make CROSS_COMPILE=/path/to/cross/compiler

upload arch/x86/boot/bzImage to as204te with Y-moden.
```

Some useful CEFDK commands
----------------------------
# mfh list
# ymodem 0x200000
# bootkernel -b 0x200000 "console=tty0 console=ttyS0,115200"