Add an xdr function for the cbfs_file header

And use it in fit.c and remove one more use of htonl.

Change-Id: Ibf18dcc0a7f08d75c2374115de0db7a4bf64ec1e
Signed-off-by: Ronald G. Minnich <rminnich@google.com>
Reviewed-on: http://review.coreboot.org/5120
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

util/cbfstool/cbfs.h

@@ -126,6 +126,9 @@ uint32_t get_cbfs_entry_type(const char *name, uint32_t default_value);
 const char *get_cbfs_entry_type_name(uint32_t type);
 uint32_t get_cbfs_compression(const char *name, uint32_t unknown);
 
+/* common.c */
+void cbfs_file_get_header(struct buffer *buf, struct cbfs_file *file);
+
 /* elfheaders.c */
 int
 elf_headers(const struct buffer *pinput,