libssh: upgrade 0.6.4 -> 0.7.1

Set the correct LIB_SUFFIX to fix QA issue for multilib:
ERROR: QA Issue: libssh: Files/directories were installed but not shipped in any package:
  /usr/lib
  /usr/lib/libssh.so
  /usr/lib/libssh_threads.so.4.5.0
  /usr/lib/libssh.so.4
  /usr/lib/libssh_threads.so.4
  /usr/lib/libssh_threads.so
  [snip]
Please set FILES such that these items are packaged. Alternatively if they are unneeded, avoid installing them or delete them within do_install.  [installed-vs-shipped]

Signed-off-by: Yi Zhao <yi.zhao@windriver.com>