ARM: dts: at91: sama5d2: fix wrong interrupt-cells property

ARM: dts: at91: sama5d2: fix wrong interrupt-cells property

The PMC node is not an interrupt provider, so it must not have
interrupt-cells.

This fixes the warning (on newer DTC):
arch/arm/dts/sama5d2.dtsi:82.22-602.6: Warning (interrupt_provider): /ahb/apb/pmc@f0014000: '#interrupt-cells' found, but node is not an interrupt provider

Fixes: 2c4b2dd289 ("ARM: at91/dt: Add device tree for SAMA5D2 Xplained")
Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
Reviewed-by: Claudiu Beznea <claudiu.beznea@microchip.com>