drm/i915/cnl: Fix LSPCON support.

drm/i915/cnl: Fix LSPCON support.

When LSPCON support was extended to CNL
one part was missed on lspcon_init.

So, instead of adding check per platform on lspcon_init
let's use HAS_LSPCON that is already there for that
purpose.

Fixes: ff15947e0f02 ("drm/i915/cnl: LSPCON support is gen9+")
Cc: Shashank Sharma <shashank.sharma@intel.com>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Shashank Sharma <shashank.sharma@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170816030403.11368-1-rodrigo.vivi@intel.com
(cherry picked from commit acf58d4e965d40fc014252292b0911b4c9fe6697)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>