gpu: pvr: fix handle allocation when sharing sync objects

gpu: pvr: fix handle allocation when sharing sync objects

This is needed by an upcoming patch fixing sync object sharing, which
requires support for multiple sync object handles pointing to the same
sync object. This will work if the handles are allocated in different
processes, but will fail if allocted within a single process. Fix this
by explicitly allowing the handle framework to allocate multiple
handles for the same object within a single process.

Signed-off-by: Imre Deak <imre.deak@nokia.com>