ARM: dts: imx6dl-prtrvt: drop undocumented TRF7970A NFC properties

Neither the bindings nor the device driver use/document
"vin-voltage-override" and "t5t-rmb-extra-byte-quirk" properties.

Cc: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>