drm/i915/tc: Remove redundant wakeref=0 check from unblock_tc_cold()

After the previous patch unblock_tc_cold() will not be called in a
disconnected mode, so the wakeref passed to it will be always non-zero.
Remove the redundant check.

Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230323142035.1432621-18-imre.deak@intel.com