conf: Remove dmix.direct_memory_access setup

conf: Remove dmix.direct_memory_access setup

The commit [22eca6468b4a: pcm: dmix: Allow disabling x86
optimizations] introduced the new flag for dmix & co,
direct_memory_access.  However, it turned out that such an addition of
the new flag in the default pcm definition causes an error when it's
used with old alsa-lib codes.  Although the code added here is
correct, per se, and it works as expected, it's not wise to break the
configuration with old stuff -- even if the usage is somehow incorrect
and should be avoided.

Since the usage of the new flag is only for HDMI LPE audio, and the
usage of dmix itself should be limited with that hardware, this patch
removes the setup so that it works with the old alsa-lib again.  We
may introduce the dmix behavior change in a smarter way, e.g. passing
some flag from the hardware driver so that it works more generically
without the manual fiddling of config files.

Bugzilla: http://bugzilla.opensuse.org/show_bug.cgi?id=1037021
Signed-off-by: Takashi Iwai <tiwai@suse.de>