IB/ipath: Misc sparse warning cleanup

Recent sparse versions and kernel cleanups knock down the false positive
rate of the ipath driver code to a point where having it be sparse clean
is worthwhile. Here we fixup the sparse warnings.  Some of these warnings
(and the impetus to run sparse again) are due to work by Roland Dreier.

Signed-off-by: Arthur Jones <arthur.jones@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>