Microchip: MEC172x Add aggregated interrupt driver

Add driver implementation and header files for a MEC172x
aggregated interrupt driver. Enable the parent(ECIA) node
to have the driver initialize interrupt hardware for use.
Enable child nodes for those GIRQs used for aggregation.
Refer to chip documention for the list of GIRQs restricted
to aggregation and those which support direct mode.
Add chip level device tree node for MEC172x EC interrupt
aggregator parent and GIRQ children. Each child node contains
a list of sources representing the source bit position in the
GIRQ registers.
Add DT bindings for ECIA and GIRQ nodes.
Add build file(s) and configuration items for the MEC172x ECIA
aggregated interrupt driver. Add and enable the MEC172x interrupt
driver on the MEC172x evaluation board(EVB). Enable parent node to
initialize ECIA hardware. Child nodes are left disabled until a
future driver needs them.

Signed-off-by: Scott Worley <scott.worley@microchip.com>