docs: virt: Convert msr.txt to ReST format

- Use document title markup;
- Convert tables;
- Add blank lines and adjust indentation.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2 files changed