Revert "dmaengine: Add a warning for drivers not using the generic slave caps retrieval"

Revert "dmaengine: Add a warning for drivers not using the generic slave caps retrieval"

This reverts commit e1d6d8ca9bca8db8281631bc081cd7d2f39a75ab.

It added a new warning to try to encourage driver writers to set the
device capabities properly, but drivers haven't been updated and in the
meantime it just generaters a scary message that users cannot actually
do anything about.

Warnings like these are appropriate if you actually expect to fix the
code that causes them.  They are not appropriate for releases.

Requested-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>