drm/amdgpu: Allow switching to CUSTOM profile on smu7 v2

Allow changing to the CUSTOM profile without requiring the
parameters being passed in each time. Store the values in
the smu7_profiling table since it's defined here anyways

v2: Add check that CUSTOM was previously set

Signed-off-by: Kent Russell <kent.russell@amd.com>
Reviewed-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>