drm/i915: Make sure i915_ggtt_view is inited when creating an FB

This probably doesn't cause an issue, since the code checks the view
type dependent size of the views before comparing them, but let's follow
the practice to bzero the whole struct when initializing it.

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210325214808.2071517-5-imre.deak@intel.com