drm/nouveau/kms/nv140-: Use hard-coded wndws or core channel for CRC channel

Originally it was assumed based on Nvidia's open-gpu-docs and testing that
NVDisplay required that at least one wndw which belongs to a given head to
be used as the controlling channel
(NVC37D_HEAD_SET_CRC_CONTROL_CONTROLLING_CHANNEL) in order for CRC capture
to function. While this is the case on Volta, Turing actually adds the
ability to instead use the core channel as the controlling channel. For
Turing this is quite useful, as it means that we can always default to the
core channel as the controlling channel and we don't need to be concerned
about ensuring we have at least one wndw channel owned by a head with CRC
output enabled. While Volta lacks this ability, Volta conveniently also
lacks flexible wndw mapping - meaning that we can always rely on each head
having four wndw channels mapped to it regardless of the atomic state.

So, simply use the hard-coded wndw mappings we're guaranteed to have on
Volta as the controlling channel, and use the core channel as the
controlling channel for Turing+. As a result this also renders the plane
ownership logic in nv50_crc_atomic_check() unnessecary, which gives us one
less thing to implement when we get support for flexible wndw mapping. We
also can entirely drop the wndw parameter from our set_src callbacks, and
the atomic state.

v2 (Karol): put prackets around complex macro definition
            removed spaces before :32 in structs

Cc: Martin Peres <martin.peres@free.fr>
Cc: Jeremy Cline <jcline@redhat.com>
Cc: Simon Ser <contact@emersion.fr>
Signed-off-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Reviewed-by: Karol Herbst <kherbst@redhat.com>
Signed-off-by: Karol Herbst <kherbst@redhat.com>
Link: https://gitlab.freedesktop.org/drm/nouveau/-/merge_requests/10