IB/addr: Add AF_IB support to ip_addr_size

Add support for AF_IB to ip_addr_size, and rename the function to
account for the change.  Give the compiler more control over whether
the call should be inline or not by moving the definition into the .c
file, removing the static inline, and exporting it.

Signed-off-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>