drm/amd/pm: fix a double-free in si_dpm_init

When the allocation of
adev->pm.dpm.dyn_state.vddc_dependency_on_dispclk.entries fails,
amdgpu_free_extended_power_table is called to free some fields of adev.
However, when the control flow returns to si_dpm_sw_init, it goes to
label dpm_failed and calls si_dpm_fini, which calls
amdgpu_free_extended_power_table again and free those fields again. Thus
a double-free is triggered.

Fixes: 841686df ("drm/amdgpu: add SI DPM support (v4)")
Signed-off-by: Zhipeng Lu <alexious@zju.edu.cn>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>