infiniband: shut up a maybe-uninitialized warning

infiniband: shut up a maybe-uninitialized warning

Some configurations produce this harmless warning when built with gcc
-Wmaybe-uninitialized:

  infiniband/core/cma.c: In function 'cma_get_net_dev':
  infiniband/core/cma.c:1242:12: warning: 'src_addr_storage.sin_addr.s_addr' may be used uninitialized in this function [-Wmaybe-uninitialized]

I previously reported this for the powerpc64 defconfig, but have now
reproduced the same thing for x86 as well, using gcc-5 or higher.

The code looks correct to me, and this change just rearranges it by
making sure we alway initialize the entire address structure to make the
warning disappear.  My first approach added an initialization at the
time of the declaration, which Doug commented may be too costly, so I
hope this version doesn't add overhead.

Link: http://arm-soc.lixom.net/buildlogs/mainline/v4.7-rc6/buildall.powerpc.ppc64_defconfig.log.passed
Link: https://patchwork.kernel.org/patch/9212825/
Acked-by: Haggai Eran <haggaie@mellanox.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>