IB/core: Make uverbs flow structure use names like verbs ones

This patch adds "flow" prefix to most of data structure added as part
of commit 436f2ad0 ("IB/core: Export ib_create/destroy_flow through
uverbs") to keep those names in sync with the data structures added in
commit 319a441d

 ("IB/core: Add receive flow steering support").

It's just a matter of translating 'ib_flow' to 'ib_uverbs_flow'.

Signed-off-by: Yann Droneaud <ydroneaud@opteya.com>
Link: http://marc.info/?i=cover.1383773832.git.ydroneaud@opteya.com
Signed-off-by: Roland Dreier <roland@purestorage.com>