DynamicTables: Fix DT PCI interrupt flags parsing

DynamicTables: Fix DT PCI interrupt flags parsing

Device Tree PCI interrupt flags use the convention described at
linux/Documentation/devicetree/bindings/interrupt-controller/arm,gic.yaml

The 3rd cell is the flags, encoded as follows:
  bits[3:0] trigger type and level flags.
  1 = low-to-high edge triggered
  2 = high-to-low edge triggered (invalid for SPIs)
  4 = active high level-sensitive
  8 = active low level-sensitive (invalid for SPIs).

Fix the incorrect code.

Signed-off-by: Pierre Gondois <Pierre.Gondois@arm.com>
Reviewed-by: Sami Mujawar <sami.mujawar@arm.com>