drm: Import drm_fixed.h from Linux 3.8
Provide human readable debug output.
Update the mis-predicted branch PMC names (for sandy bridge) to not clash.

The SDM (June 2013) tables on these are rather confusing.  Yes, they
assign the same name (BR_MISP_RETIRED.ALL_BRANCHES) to two codes
(C5H/00H and C5H/04H.) The latter however is the PEBS version.

So, to make it easier to see the difference - and yes, we can use
both without having to actually enable the PEBS specific bits! -
just rename the PEBS one to _PS so there's no clashing.

Tested:

* Sandy bridge