Add missing MSRs for powertop

I reported this same bug on the powertop bugtracker [1] because I think both projects need to change something here.

When running powertop it crashes and prints:

  unknown op '{'
                read_msr cpu0 0xe8 : Input/output error

It seems that powertop is trying to access model specific registers and because qemu doesn't emulate them it crashes.
Clearly powertop shouldn't crash in such case but I think it would also be better if qemu could add support for these registers.

1: https://app.devzing.com/powertopbugs/bugzilla/show_bug.cgi?id=4