drm/nouveau: Remove duplicate ACPI_VIDEO_NOTIFY_PROBE definition

Commit 3a6536c5 ("drm/nouveau: Intercept ACPI_VIDEO_NOTIFY_PROBE")
added a definition of ACPI_VIDEO_NOTIFY_PROBE because <acpi/video.h> didn't
supply one.  Later, commit eff4a751

 ("ACPI / video: Move
ACPI_VIDEO_NOTIFY_* defines to acpi/video.h") moved ACPI_VIDEO_NOTIFY_PROBE
and other definitions to <acpi/video.h>, so the copy in nouveau_display.c
is now unnecessary.

Remove the unnecessary definition from nouveau_display.c.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: Hans de Goede <hdegoede@redhat.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>