sound fixes for 3.18-rc3

Although the diffstat looks scary, it's just because of the removal of
the dead code (s6000), thus it must not affect anything serious.
Other than that, all small fixes.  The only core fix is zero-clear for
a PCM compat ioctl.  The rest are driver-specific, bebob, sgtl500,
adau1761, intel-sst, ad1889 and a few HD-audio quirks as usual.
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