IB/core: Remove IB_DEVICE_SEND_W_INV capability flag

In 2.6.26, we added some support for send with invalidate work
requests, including a device capability flag to indicate whether a
device supports such requests.  However, the support was incomplete:
the completion structure was not extended with a field for the key
contained in incoming send with invalidate requests.

Full support for memory management extensions (send with invalidate,
local invalidate, fast register through a send queue, etc) is planned
for 2.6.27.  Since send with invalidate is not very useful by itself,
just remove the IB_DEVICE_SEND_W_INV bit before the 2.6.26 final
release; we will add an IB_DEVICE_MEM_MGT_EXTENSIONS bit in 2.6.27,
which makes things simpler for applications, since they will not have
quite as confusing an array of fine-grained bits to check.

Signed-off-by: Roland Dreier <rolandd@cisco.com>