drm/i915: Eliminate IS_MTL_GRAPHICS_STEP

Several workarounds are guarded by IS_MTL_GRAPHICS_STEP.  However none
of these workarounds are actually tied to MTL as a platform; they only
relate to the Xe_LPG graphics IP, regardless of what platform it appears
in.  At the moment MTL is the only platform that uses Xe_LPG with IP
versions 12.70 and 12.71, but we can't count on this being true in the
future.  Switch these to use a new IS_GFX_GT_IP_STEP() macro instead
that is purely based on IP version.  IS_GFX_GT_IP_STEP() is also
GT-based rather than device-based, which will help prevent mistakes
where we accidentally try to apply Xe_LPG graphics workarounds to the
Xe_LPM+ media GT and vice-versa.

v2:
 - Switch to a more generic and shorter IS_GT_IP_STEP macro that can be
   used for both graphics and media IP (and any other kind of GTs that
   show up in the future).
v3:
 - Switch back to long-form IS_GFX_GT_IP_STEP macro.  (Jani)
 - Move macro to intel_gt.h.  (Andi)
v4:
 - Build IS_GFX_GT_IP_STEP on top of IS_GFX_GT_IP_RANGE and
   IS_GRAPHICS_STEP building blocks and name the parameters from/until
   rather than begin/fixed.  (Jani)
 - Fix usage examples in comment.
v5:
 - Tweak comment on macro.  (Gustavo)

Cc: Gustavo Sousa <gustavo.sousa@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Andi Shyti <andi.shyti@linux.intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230821180619.650007-15-matthew.d.roper@intel.com