gpu: pvr: Reuse the same syncobject across all wraps

gpu: pvr: Reuse the same syncobject across all wraps

Create a hash table and store all the syncobjects that we create for
wrapped memory using the address of the buffer as the key. When a wrap
happens we check the hash table to see if the buffer has already been
wrapped and if so we retrieve the sync object and reuse it. When the
last wrap that is using a syncobject is freed then we remove the
syncobject from the hash table and free it.

Signed-off-by: Mark Underwood <mark.underwood@imgtec.com>
Signed-off-by: Imre Deak <imre.deak@nokia.com>