drm/xe: Remove dependency on intel_gt_regs.h

Create regs/xe_gt_regs.h file with all the registers and bit
definitions used by the xe driver. Eventually the registers may be
defined in a different way and since xe doesn't supported below gen12,
the number of registers touched is much smaller, so create a new header.

The definitions themselves are direct copy from the
gt/intel_gt_regs.h file, just sorting the registers by address.
Cleaning those up and adhering to a common coding style is left for
later.

v2: Make the change to MCR_REG location in a separate patch to go
    through the i915 branch  (Matt Roper / Rodrigo)

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>