drm/i915: Name our BARs based on the spec

drm/i915: Name our BARs based on the spec

We use all kinds of weird names for our base address registers.
Take the names from the spec and stick to them to avoid confusing
everyone.

The only exceptions are IOBAR and LMEMBAR since naming them
IOBAR_BAR and LMEMBAR_BAR looks too funny, and yet I think
that adding the _BAR to GTTMMADR & co. (which don't have one
in the spec name) does make it more clear what they are.
And IOBAR vs. GTTMMADR_BAR also looks a bit too inconsistent
for my taste.

v2: Fix gvt build
v3: Add GEN2_IO_BAR for completeness

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221005195646.17201-1-ville.syrjala@linux.intel.com
Acked-by: Matthew Auld <matthew.auld@intel.com>