x86 PAT memtype regression fixes

[Dave Airlie]

This is the working set, I messed up a git add on CONFIG_PAT vs
CONFIG_X86_PAT. This set of changes fixes a regression since
the change to the pfn_insert_mixed code to use the memtype tracking
code.

All the GPU drivers using TTM need to insert the VRAM mapping
into the memtype table so don't get UC mappings for lots of things.

Dave.