import v3.15.5.

* import v3.15.5.
* import rtl8192du into staging:
  5d7c8d0ef70db822b0e211d9c6a325dd3d321732
  Merge branch 'kernel-version' of http://github.com/lwfinger/rtl8192du
  into kernel-version
  e26803d9771e72c28a7f0a9f6fae2984f436bd18
  rtl8192du: Fix some sparse warnings
NOT RELEASED YET

* NOT RELEASED YET
* set ABI to 5.slh.2.