drm/i915/icl: reverse uninit order

Bspec 21257 says "DDIA PHY is the comp master, so it must
not be un-initialized if other combo PHYs are in use". Here
we are shutting down all phys, so it's not strictly required.
However let's be consistent on deinitializing things in the
reversed order we initialized them.

v2: simplify protection for enum port being unsigned in future
v3: spell out reverse rather than rev

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181114011509.3667-2-lucas.demarchi@intel.com