drm/i915/display/tc: Rename safe_mode functions ownership

When DP_PHY_MODE_STATUS_NOT_SAFE is set, it means that display
has the control over the TC phy.
The "not safe" naming is confusing using ownership make it easier
to read also future platforms will have a new register that does the
same job as DP_PHY_MODE_STATUS_NOT_SAFE but with the onwership name.

BSpec: 49294
Cc: Imre Deak <imre.deak@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Clinton Taylor <Clinton.A.Taylor@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210514153711.2359617-10-matthew.d.roper@intel.com