ARCv2: IDU-intc: Delete deprecated parameters in Device Trees

No need for specifying a list of interrupts in the declaration
of IDU interrupt controller anymore since the kernel can obtain
a number of supported interrupts from the build register.

Also delete support of the second parameter for devices which
are connected to IDU because it is not used anywhere.

Signed-off-by: Yuriy Kolerov <yuriy.kolerov@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>