fdt: Fix dt memreserve entry ...

The fdt reserve map needs address/size values, not address/end values
like accidently done for generating the reserve entry for the dt.

Reported-by: Jürgen Beisert <j.beisert@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

of: remove unused libfdt ...

Now that we are completely independent of libfdt remove the unused
code.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

of: Add reservemap handling ...

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

of: move flat devicetree functions to separate file ...

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>