Move to fully dynamic UAR mode once user space supports it.  In this case
we prevent any legacy mode of UARs on the allocated context and prevent
redundant allocation of the static ones.

Link: https://lore.kernel.org/r/20200324060143.1569116-6-leon@kernel.orgSigned-off-by: NYishai Hadas <yishaih@mellanox.com>
Reviewed-by: NMichael Guralnik <michaelgur@mellanox.com>
Signed-off-by: NLeon Romanovsky <leonro@mellanox.com>
Signed-off-by: NJason Gunthorpe <jgg@mellanox.com>