drm/nvc0/copy: check PUNITS to determine which copy engines are disabled

drm/nvc0/copy: check PUNITS to determine which copy engines are disabled

commit 14f0458a41e033dee31ba605137419385c03fc78 upstream.

On some Fermi chipsets (NVCE particularly) PCOPY1 doesn't exist.  And if
what I've seen on Kepler is true of Fermi too, chipsets of the same type
can have different PCOPY units available.

This should fix a v3.5 regression reported by a number of people effecting
suspend/resume on NVC8/NVCE chipsets.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>