x86: move per CPU microcode structure declaration to header file

This structure will be later used by other modules as well and
needs therfore to be moved out to a header file.

Signed-off-by: Peter Oruba <peter.oruba@amd.com>
Cc: Tigran Aivazian <tigran@aivazian.fsnet.co.uk>
Signed-off-by: Ingo Molnar <mingo@elte.hu>