ARM: at91: dts: sama5d3: change name of pinctrl of ISI_MCK

For sama5d3xmb board, the pins: pinctrl_isi_pck_as_mck is pck1, and
used to provide MCK for camera sensor.

We change its name to: pinctrl_pck1_as_isi_mck.

As we want camera sensor instead of ISI to configure the pck1 (ISI_MCK) pin.
So we remove this pinctrl from ISI DT node. It will be added in 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>