Revert "Add implementation of poll() to dma_buf using KDS"

Revert "Add implementation of poll() to dma_buf using KDS"

This reverts commit 5d1bb28fa72400006b3956ab7d869dffd091af23.

There are no users of dma-buf poll(), this isn't upstream, and we aren't
carrying it forward to 3.8.

Revert from 3.4 to keep 3.8 & 3.4 more consistent.

Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
BUG=none
TEST=none

Change-Id: Ia6628aef06f5ee228f3ac479bfa0e75b45573f04
Reviewed-on: https://gerrit.chromium.org/gerrit/50187
Tested-by: Daniel Kurtz <djkurtz@chromium.org>
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>
Commit-Queue: Daniel Kurtz <djkurtz@chromium.org>
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>