linux-arm: disable tree vectorization when neon fpu is used

Always disable tree vectorization on neon devices due
to a slight performance degredation when neon fpu is
utilized. This may be fixed in compiler at some point.

Source: https://wiki.debian.org/ArmHardFloatPort/VfpComparison#NEON

Change-Id: I154319b5437992ec7d4c5f452c99569add4e7bec