The struct holding device driver data contained both read only(ro)
and read write(rw) fields.

Separating ro fields from rw fields was recommended as
a preferable design pattern during review[1].

Group ro fields into a separate const struct. Associate it to
the miscdevice being registered by keeping its pointer in the
same container struct as the miscdevice.

Link: https://lore.kernel.org/lkml/Y+9H9otxLYPqMkUh@kroah.com/ [1]
Signed-off-by: Jithu Joseph <jithu.joseph@intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Link: https://lore.kernel.org/r/20230322003359.213046-3-jithu.joseph@intel.comReviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>