IntelSiliconPkg: IOMMU generic bug fix

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2401



Looks like Addresswidth is BIT wise values.
Right now these values are not used any.

Suggested-by: Star Zeng <star.zeng@intel.com>
Signed-off-by: Lorena R De Leon Vasquez <lorena.r.de.leon.vasquez@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>