drm/connector: Allow max possible encoders to attach to a connector

Currently we restrict the number of encoders that can be linked to
a connector to 3, increase it to match the maximum number of encoders
that can be initialized(32).

To more effiently do that lets switch from an array of encoder ids to
bitmask.

v2: Fixing missed return on amdgpu_dm_connector_to_encoder()

Suggested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: dri-devel@lists.freedesktop.org
Cc: intel-gfx@lists.freedesktop.org
Cc: nouveau@lists.freedesktop.org
Cc: amd-gfx@lists.freedesktop.org
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190913232857.389834-2-jose.souza@intel.com