nfc: pn533: i2c: "pn532" as dt compatible string

It is favourable to have one unified compatible string for devices that
have multiple interfaces. So this adds simply "pn532" as the devicetree
binding compatible string and makes a note that the old ones are
deprecated.

Cc: Johan Hovold <johan@kernel.org>
Cc: Simon Horman <horms@verge.net.au>
Signed-off-by: Lars Poeschel <poeschel@lemonage.de>
Signed-off-by: David S. Miller <davem@davemloft.net>