DynamicTablesPkg: Add frame number validation to GTDT generator

Added code to check if the Generic Timer Block Structure's frame number
provided by the platform repository is within the allowed range (0-7).

References:
- ACPI 6.2 Errata A, Table 5-122, September 2017

Signed-off-by: Krzysztof Koch <krzysztof.koch@arm.com>
Reviewed-by: Alexei Fedorov <Alexei.Fedorov@arm.com>
Reviewed-by: Sami Mujawar <sami.mujawar@arm.com>

DynamicTablesPkg/Library/Acpi/Arm/AcpiGtdtLibArm/GtdtGenerator.c

@@ -218,6 +218,15 @@ AddGTBlockTimerFrames (
       GtBlockFrame
       ));
 
+    if (GTBlockTimerFrameList->FrameNumber >= 8) {
+      DEBUG ((
+        DEBUG_ERROR,
+        "ERROR: GTDT: Frame number %d is not in the range 0-7\n",
+        GTBlockTimerFrameList->FrameNumber
+      ));
+      return EFI_INVALID_PARAMETER;
+    }
+
     GtBlockFrame->GTFrameNumber = GTBlockTimerFrameList->FrameNumber;
     GtBlockFrame->Reserved[0] = EFI_ACPI_RESERVED_BYTE;
     GtBlockFrame->Reserved[1] = EFI_ACPI_RESERVED_BYTE;