drm/amdgpu: Delete a variable in amdgpu_cgs_acpi_eval_object()

The local variable "func_no" was assigned a value at two places.
But it was not read within this function. Thus delete it.

Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>