util/cbfstool: Use %zu instead of %ld for size_t arguments

cbfstool fails to built under 32-bit platforms since commit

    aa2f739a cbfs: fix issues with word size and endianness.

due to the use of '%ld' format specifier on size_t, which on these
platforms is only 32-bit.

No error is seen though, when cbfstool is built, when building a coreboot
image, where it is put in `build/cbfstool`.

Use the length modifier `z` for size_t arguments, and cast to size_t where
appropriate.

Change-Id: Id84a20fbf237376a31f7e4816bd139463800c977
Signed-off-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-on: http://review.coreboot.org/5388
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@gmail.com>

util/cbfstool/elfheaders.c

@@ -147,7 +147,7 @@ check_size(const struct buffer *b, size_t offset, size_t size, const char *desc)
 
 	if (offset >= buffer_size(b) || (offset + size) > buffer_size(b)) {
 		ERROR("The file is not large enough for the '%s'. "
-		      "%ld bytes @ offset %zu, input %zu bytes.\n",
+		      "%zu bytes @ offset %zu, input %zu bytes.\n",
 		      desc, size, offset, buffer_size(b));
 		return -1;
 	}