## Description
Cherry-pick from release/202202 (commit
[d484285](d484285210)).
Read FV header length from the header instead of using
`sizeof(EFI_FIRMWARE_VOLUME_HEADER)` to account for variable number
of block map entries.
- [x] Impacts functionality?
- **Functionality** - Does the change ultimately impact how firmware
functions?
- Examples: Add a new library, publish a new PPI, update an algorithm,
...
- [ ] Impacts security?
- **Security** - Does the change have a direct security impact on an
application,
flow, or firmware?
- Examples: Crypto algorithm change, buffer overflow fix, parameter
validation improvement, ...
- [ ] Breaking change?
- **Breaking change** - Will anyone consuming this change experience a
break
in build or boot behavior?
- Examples: Add a new library class, move a module to a different repo,
call
a function in a new library class in a pre-existing module, ...
- [ ] Includes tests?
- **Tests** - Does the change include any explicit test code?
- Examples: Unit tests, integration tests, robot tests, ...
- [ ] Includes documentation?
- **Documentation** - Does the change contain explicit documentation
additions
outside direct code modifications (and comments)?
- Examples: Update readme file, add feature readme file, link to
documentation
on an a separate Web page, ...
## How This Was Tested
(cherry-pick from release/202202)
## Integration Instructions
N/A other than including this change.