Prepare for next patches (Improving BKDG implementation of P-states,

Prepare for next patches (Improving BKDG implementation of P-states,
CPU and northbridge frequency and voltage
handling for Fam 10 in SVI mode).

No change of behaviour intended.

Refactor FAM10 fidvid . prep_fid_change was already long and it'd
get longer with forthcoming patches. We now take apart F3xA0,
Power Control Misc Register to its own function.

Signed-off-by: Xavi Drudis Ferran <xdrudis@tinet.cat>
Acked-by: Marc Jones <marcj303@gmail.com>
git-svn-id: svn://svn.coreboot.org/coreboot/trunk@6389 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1