arm64: dts: intel: socfpga_agilex: use defined for GIC interrupts

Use human-readable defines for GIC interrupt type and flag, instead of
hard-coding the numbers.  It makes review easier.  No functional change.

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>