thunderbolt: Rename Intel TB_VSE_CAP_IECS capability

Rename the VSC capability: TB_VSE_CAP_IECS to TB_VSE_CAP_CP_LP to follow
the Intel devices namings as appear in the datasheet. This capability
is used for controlling CLx (Low Power states of the link).

Signed-off-by: Gil Fine <gil.fine@intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>