octeontx2-af: Add a 'rvu_free_bitmap()' function

In order to match 'rvu_alloc_bitmap()', add a 'rvu_free_bitmap()' function

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>