drm/xe: Introduce xe_reg/xe_reg_mcr

drm/xe: Introduce xe_reg/xe_reg_mcr

Stop using i915 types for registers. Use our own types. Differently from
i915, this will keep under the register definition the knowledge for the
different types of registers. For now, the "flags"/"options" are mcr and
masked, although only the former is being used.

Additionally MCR registers have their own type. The only place that
should really look inside a xe_mcr_reg_t is that code dealing with the
steering and using other APIs when the register is MCR has been a source
of problem in the past.

Most of the driver is agnostic to the register differences since they
either use the definition from the header or already call the correct
MCR_REG()/_MMIO() macros. By embeding the struct xe_reg inside the
struct it's also possible to guarantee the compiler will break if
using RANDOM_MCR_REG.reg is attempted, since now the u32 is inside the
inner struct.

v2:
  - Deep a dedicated type for MCR registers to avoid misuse
    (Matt Roper, Jani)
  - Drop the typedef and just use a struct since it's not an opaque type
    (Jani)
  - Add more kernel-doc
v3:
  - Use only 22 bits for the register address since all the platforms
    supported so far have only 4MB of MMIO per tile  (Matt Roper)

Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://lore.kernel.org/r/20230427223256.1432787-7-lucas.demarchi@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>