dumpimage: fit: extract FIT images

dumpimage: fit: extract FIT images

The dumpimage is able to extract components contained in a FIT image:

  $ ./dumpimage -T flat_dt -i CONTAINER.ITB -p INDEX FILE

The CONTAINER.ITB is a regular FIT container file. The INDEX is the poisition
of the sub-image to be retrieved, and FILE is the file (path+name) to save the
extracted sub-image.

For example, given the following kernel.its to build a kernel.itb:

  /dts-v1/;
  / {
      ...
      images {
        kernel@1 {
          description = "Kernel 2.6.32-34";
          data = /incbin/("/boot/vmlinuz-2.6.32-34-generic");
          type = "kernel";
          arch = "ppc";
          os = "linux";
          compression = "gzip";
          load = <00000000>;
          entry = <00000000>;
          hash@1 {
            algo = "md5";
          };
        };
        ...
      };
      ...
    };

The dumpimage can extract the 'kernel@1' node through the following command:

  $ ./dumpimage -T flat_dt -i kernel.itb -p 0 kernel
  Extracted:
   Image 0 (kernel@1)
    Description:  Kernel 2.6.32-34
    Created:      Wed Oct 22 15:50:26 2014
    Type:         Kernel Image
    Compression:  gzip compressed
    Data Size:    4040128 Bytes = 3945.44 kB = 3.85 MB
    Architecture: PowerPC
    OS:           Linux
    Load Address: 0x00000000
    Entry Point:  0x00000000
    Hash algo:    md5
    Hash value:   22352ad39bdc03e2e50f9cc28c1c3652

Which results in the file 'kernel' being exactly the same as '/boot/vmlinuz-2.6.32-34-generic'.

Signed-off-by: Guilherme Maciel Ferreira <guilherme.maciel.ferreira@gmail.com>