drm/nouveau: Rename acpi_work to hpd_work

We need to call drm_helper_hpd_irq_event() on resume to properly detect
monitor connection / disconnection on some laptops. For runtime-resume
(which gets called on resume from normal suspend too) we must call
drm_helper_hpd_irq_event() from a workqueue to avoid a deadlock.

Rename acpi_work to hpd_work, and move it out of the #ifdef CONFIG_ACPI
blocks to make it suitable for generic work.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>