shell: update position of surfaces with type none on map()

shell: update position of surfaces with type none on map()

Needed for implementing drag'n'drop icons. When a drag starts, the
compositor will position the top-left corner of the client supplied
icon surface at the cursor hotspot. On the first attach to that
surface, the client may want to reposition it but shell->map did not
take sx and sy parameters.

This changes shell->map interface to take sx and sy parameters and
change dekstop shell implementation to update the position of a
surface of type none according to those parameters. Since a surface
of type none won't actually be mapped, the effect of this change is
only visible for surfaces that are made visible by the compositor.

Signed-off-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>