drm/nouveau/clock: fix support for more than 2 monitors on nve0

Fixes regression introduced in commit 70790f4f


"drm/nouveau/clock: pull in the implementation from all over the place"

When code was moved from nv50_crtc_set_clock to nvc0_clock_pll_set,
the PLLs it is used for got limited to only the first two VPLLs.

nv50_crtc_set_clock was only called to change VPLLs, so it didn't
limit what it was used for in any way. Since nvc0_clock_pll_set is
used for all PLLs, it has to specify which PLLs the code is used for,
and only listed the first two VPLLs.

Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=58735

This patch is a -stable candidate for 3.7.

Signed-off-by: Aleksi Torhamo <aleksi@torhamo.net>
Tested-by: Aleksi Torhamo <aleksi@torhamo.net>
Tested-by: Sean Santos <quantheory@gmail.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Cc: stable@vger.kernel.org