Work around MEMERASE ioctl for rk3066 compatibility

Due to a kernel bug and no available sources we have to work around the
MEMERASE ioctl - if used, it hangs and never returns. I straced the original
recovery executable and could see that it is simply calling write() with a
bunch of zeroes instead of using MEMERASE.

Added a hack that does the same and it seems the resulting image seems
to work.