* Remove SPEC declarations from mk/spec
* Remove all board-specific REQUIRE declaratiions left
* Replace [have_spec <board>] run-script declarations with have_board where necessary
* Remove addition of BOARD variable to SPECS in toplevel Makefile
* Move board-specific directories in base-hw out of specs
* Fix GIC model to support priority and cpu target settings correspondingly
* Fix semantic of SGIR register for GICv2
* Minor GIC model IRQ state fix
* Introduce synchronization for VirtIO and GIC models
* Enable multiple CPUs in test run-script for ARMv8
Fix#3926