ARM: dts: at91: sama5d2_som1_ek: disable ISC node by default

Without a sensor node, the ISC will simply fail to probe, as the
corresponding port node is missing.
It is then logical to disable the node in the devicetree.
If we add a port with a connection to a sensor endpoint, ISC can be enabled.

Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Link: https://lore.kernel.org/r/20210902121358.503589-1-eugen.hristev@microchip.com