Add a new function to find a port on a device given a GID by searching the
cached GID tables.  Document all cache functions in ib_cache.h.  Rename
existing functions to better match format of verb routines.

Signed-off by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <roland@topspin.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>