sched: Remove debug WARN_ONCE messages

If flow control functionality is not enabled in traffic controller
userspace modules, WARN_ONCE messages are triggered. Note that qdisc
will still be setup even if these debug messages are logged.
Remove these messages to reduce log spam.

CRs-Fixed: 2053221
Change-Id: I62a2fcb30d19579180b3df16f33953546f94511a
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>