MdeModulePkg: Add IOMMU protocol NULL check

[AMI-HankLin]

Add IOMMU protocol null check before call IOMMU protocol functions. This avoids IOMMU protocol function pointers is NULL.

Sign-off-by: Hank Lin hanklin@ami.com

Description

Because IOMMU protocol may be NULL in some situation so that it need to add IOMMU protocol null check mechanism before call IOMMU protocol functions.

For details on how to complete these options and their meaning refer to CONTRIBUTING.md.

• Impacts functionality?
• Impacts security?
• Breaking change?
• Includes tests?
• Includes documentation?

How This Was Tested

Let BIOS not to install IOMMU protocol and system should not assert

Integration Instructions

N/A

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[AMI-HankLin]

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