drm/i915/mst: Continue state updates even if AUX writes fail.

We are too late in the enabling sequence to back out cleanly, not updating
state tracking variables, like intel_dp->active_mst_links in this
instance, results in incorrect behaviour further along.

v2: Fixed int v/s bool comparison

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Nathan Ciobanu <nathan.d.ciobanu@linux.intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107281


Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Reviewed-by: Nathan Ciobanu <nathan.d.ciobanu@linux.intel.com>
Tested-by: Nathan Ciobanu <nathan.d.ciobanu@linux.intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180718171943.3246-2-dhinakaran.pandiyan@intel.com