a minor null-ptr dereference issue

[asurati]

initialize_fdt allocates a buffer to read the dtb file, like so:

p = malloc(st.st_size);

But, if p == NULL, kexec does not exit (it does print an error); instead, it moves on with reading of the file.

[asurati]

Likewise within dtc_resize for the failure to allocated fdt.