Merge branch 'stmmac-Frame-Preemption-fixes'

Jose Abreu says:

====================
net: stmmac: Frame Preemption fixes

Two single fixes for the -next tree for recently introduced Frame Preemption
feature.

1) and 2) fixes the disabling of Frame Preemption that was not being correctly
handled because of a missing return.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>