Fix regression caused by commit b072e53b, which breaks loading nouveau
driver on optimus laptops.

On some platforms, ACPI _DSM method (nouveau_op_dsm_muid, function 0)
has special requirements on the fourth parameter, which is different
from ACPI specifications. So revert to the private implementation
to check availability of _DSM functions instead of using common
acpi_check_dsm() interface.

Fixes: b072e53b (ACPI / nouveau: replace open-coded _DSM code with helper functions)
Reported-and-tested-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>
[rjw: Subject]
Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>