drm/nouveau/fb: use correct ram oclass for nv1a hardware

commit 8613e731
Author: Ben Skeggs <bskeggs@redhat.com>
Date:   Mon Oct 21 08:50:25 2013 +1000

    drm/nouveau/fb: remove ram oclass argument from base fb constructor

Introduced a unfortunate regression by using nv10 ram oclass for nv1a
hardware, causing corruption and eventually system lockup.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=74866


Reported-by: John F. Godfrey <jfgodfrey@gmail.com>
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Cc: stable@vger.kernel.org # 3.13+
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>