IB/{core,uverbs}: Move ib_umem_xxx functions from ib_core to ib_uverbs

The next patch will add dependency from ib_umem_get in to ib_uverbs so
move the required ib_umem_xxx functionality to it's correct module -
ib_uverbs - and avoid circular dependecy from the form of ib_core ->
ib_uverbs -> ib_core in depmod.

Since this now requires all drivers to be build modular if uverbs is
modular, hoist the test a couple drivers had into the main kconfig and
apply it to all drivers uniformly.

Signed-off-by: Shamir Rabinovitch <shamir.rabinovitch@oracle.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>