fdtdump: Discourage use of fdtdump

fdtdump is, and always has been, a quick-and-dirty debugging tool.  However
I keep getting reports of people using it for real work.  For production
decompiling of a dtb, dtc in -I dtb -O dts mode is the right tool. In the
hopes of getting that message out there, add a warning message to fdtdump
to discourage its use.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

fdtdump.c

@@ -183,6 +183,11 @@ int main(int argc, char *argv[])
 	bool scan = false;
 	off_t len;
 
+	fprintf(stderr, "\n"
+"**** fdtdump is a low-level debugging tool, not meant for general use.\n"
+"**** If you want to decompile a dtb, you probably want\n"
+"****     dtc -I dtb -O dts <filename>\n\n"
+		);
 	while ((opt = util_getopt_long()) != EOF) {
 		switch (opt) {
 		case_USAGE_COMMON_FLAGS