ARM: at91: dts: sama5d3: change name of pinctrl_isi_{power,reset}

For sama5d3xmb board, the pins: pinctrl_isi_{power,reset} is used to
power-down or reset camera sensor.
So we should let camera sensor instead of ISI to configure the pins.

This patch will change pinctrl name from pinctrl_isi_{power,reset} to
pinctrl_sensor_{power,reset}. And remove these two pinctrl from ISI's
DT node. We will add these two pinctrl to sensor's DT node.

Signed-off-by: Josh Wu <josh.wu@atmel.com>
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>