ARM: dts: imx6: rdu2: Disable WP for USDHC2 and USDHC3

[ Upstream commit cd58a174e58649426fb43d7456e5f7d7eab58af1 ]

RDU2 production units come with resistor connecting WP pin to
correpsonding GPIO DNPed for both SD card slots. Drop any WP related
configuration and mark both slots with "disable-wp".

Reported-by: Chris Healy <cphealy@gmail.com>
Reviewed-by: Chris Healy <cphealy@gmail.com>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Shawn Guo <shawnguo@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>