drm/i915/uapi: convert i915_query and friend to kernel doc

drm/i915/uapi: convert i915_query and friend to kernel doc

Add a note about the two-step process.

v2(Tvrtko):
  - Also document the other method of just passing in a buffer which is
    large enough, which avoids two ioctl calls. Can make sense for
    smaller query items.
v3: prefer kernel-doc references for structs and members

Suggested-by: Daniel Vetter <[email protected]>
Signed-off-by: Matthew Auld <[email protected]>
Cc: Joonas Lahtinen <[email protected]>
Cc: Tvrtko Ursulin <[email protected]>
Cc: Jordan Justen <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: Kenneth Graunke <[email protected]>
Cc: Jason Ekstrand <[email protected]>
Cc: Dave Airlie <[email protected]>
Cc: [email protected]
Cc: [email protected]
Reviewed-by: Daniel Vetter <[email protected]>
Reviewed-by: Jason Ekstrand <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]