drm/amd/pm: Remove unused smu_mode2_reset_is_support

smu_mode2_reset_is_support() was added in 2020 by
commit 5c03e584 ("drm/amdgpu:add smu mode1/2 support for aldebaran")
but has remained unused.

See discussion at:
https://lore.kernel.org/all/DM4PR12MB5165D85BD85BC8FC8BF7A3B48E88A@DM4PR12MB5165.namprd12.prod.outlook.com/



Remove it.

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>