util/cbfstool: Support FIT payloads

In order to support booting a GNU/Linux payload on non x86, the FIT format
should be used, as it is the defacto standard on ARM.
Due to greater complexity of FIT it is not converted to simple ELF format.

Add support for autodecting FIT payloads and add them as new CBFS_TYPE 'fit'.
The payload is included as is, with no special header.
The code can determine the type at runtime using the CBFS_TYPE field.
Support for parsing FIT payloads in coreboot is added in a follow on
commit.
Compression of FIT payloads is not supported, as the FIT sections might be
compressed itself.

Starting at this point a CBFS payload/ can be either of type FIT or SELF.

Tested on Cavium SoC.

Change-Id: Ic5fc30cd5419eb76c4eb50cca3449caea60270de
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/25860
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>

payloads/libpayload/include/cbfs_core.h

@@ -68,6 +68,7 @@
 
 #define CBFS_TYPE_STAGE      0x10
 #define CBFS_TYPE_SELF       0x20
+#define CBFS_TYPE_FIT        0x21
 #define CBFS_TYPE_OPTIONROM  0x30
 #define CBFS_TYPE_BOOTSPLASH 0x40
 #define CBFS_TYPE_RAW        0x50