nvc0: add documentation for nve4+ (Kepler) COPY class

nvc0: add documentation for nve4+ (Kepler) COPY class

Has been utilised within nouveau in place of the former M2MF class, which was
dropped for Kepler in PGRAPH in favour of:

  - a new P2MF object that only does simple upload; and
  - PCOPY took over responsibility of M2MF's other DMA functions.

Autogenerated headers from envytools commit 32659e654170cb03038ccf2cb165decd3a2409d6

NVIDIA documentation released at:
  https://github.com/NVIDIA/open-gpu-doc/blob/master/classes/dma-copy/cla0b5.h

Signed-off-by: Rhys Kidd <rhyskidd@gmail.com>
Reviewed-by: Karol Herbst <kherbst@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5982>