drm/amd/amdgpu: Fix memleak in cz_parse_power_table()

If one of the entries fails to be allocated then free
all of the previous entries before freeing the array which
holds their pointers.

Signed-off-by: Tom St Denis <tom.stdenis@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>