dev-arm: add Watchdog Module SP805 model

This provides a model of the Arm Watchdog Module SP805. This is based
on the public TRM rev. r1p0 (ARM DDI 0270B). Integration test harness
is not supported. Auto-generation of device tree entries is provided.

Change-Id: I6157cec2212d0a1d2685bcfa983d2acbae1f3377
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/24205
Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/dev/arm/SConscript

@@ -81,6 +81,7 @@ if env['TARGET_ISA'] == 'arm':
     Source('smmu_v3_slaveifc.cc');
     Source('smmu_v3_transl.cc');
     Source('timer_sp804.cc')
+    Source('watchdog_sp805.cc')
     Source('gpu_nomali.cc')
     Source('pci_host.cc')
     Source('rv_ctrl.cc')
@@ -104,6 +105,7 @@ if env['TARGET_ISA'] == 'arm':
     DebugFlag('RVCTRL')
     DebugFlag('SMMUv3')
     DebugFlag('SMMUv3Hazard')
+    DebugFlag('Sp805')
     DebugFlag('EnergyCtrl')
     DebugFlag('UFSHostDevice')
     DebugFlag('VGIC')