MLBEDSW-9774: Fix to not accept first weight buffering scheme when preBuffering depth is 16

Currrent behaviour gives up on double buffering tensors if the pre-buffering slice happens to be the minimal one. This patch makes sure that we also try to reduce the bufferingDepth before we give up in such a situation.

Change-Id: I6f52ea7b74d18863668c533f0d37bd9b6d05deb8
Signed-off-by: William Isaksson <william.isaksson@arm.com>