loader: fix incorrect alignment for ELF notes

[zhuangel]

Fix incorrect alignment for ELF notes, starting address of name field and descriptor field have a 4-byte alignment.

See refer from:

• 'Note Section' of 'Executable and Linking Format (ELF) Specification' v1.2.
• Linux implementations, https://elixir.bootlin.com/linux/v6.1/source/include/linux/elfnote.h#L56

Fixes: #71

Reported-by: Iulian Barbu iul@amazon.com
Signed-off-by: Yong He alexyonghe@tencent.com
Co-authored-by: Rob Bradford robert.bradford@intel.com
Signed-off-by: Yong He alexyonghe@tencent.com

Summary of the PR

Please summarize here why the changes in this PR are needed.

Requirements

Before submitting your PR, please make sure you addressed the following
requirements:

• All commits in this PR are signed (with git commit -s), and the commit
  message has max 60 characters for the summary and max 75 characters for each
  description line.
• All added/changed functionality has a corresponding unit/integration
  test.
• All added/changed public-facing functionality has entries in the "Upcoming
  Release" section of CHANGELOG.md (if no such section exists, please create one).
• Any newly added unsafe code is properly documented.

[rbradford]

Looks good, did you test with with a VMM and an kernel you were having issues with?

[zhuangel]

Looks good, did you test with with a VMM and an kernel you were having issues with?

Thanks for reviewing, I was tested the issue with the revise code in local it solve the issue.

Then I re-run the test with formal way, cloud-hypervisor v29.0, revise linux-loader in Cargo.toml into linux-loader = { git = "https://github.com/zhuangel/linux-loader", branch = "alexyonghe/dev", features = ["elf", "bzimage", "pe"] }, I cloud load kernel v6.1 successfully (as compare, directly run the test with cloud-hypervisor v29.0, load failed with ApiError(VmBoot(KernelMissingPvhHeader))).