ARM: dts: imx7d-sdb: Fix watchdog and pwm pinmux

The watchdog pin and the pwm output pin are controlled by the
iomuxc_lpsr, not the regular iomux, so move the pins there.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>