Call ether_input/m_freem without holding a lock or referencing unnecessary objects

When NET_MPSAFE on, a bridge tries to pass up a packet to Layer 3
(or call m_freem) with holding a lock or referencing unnecessary
objects. That causes random lock ups. The change fixes the issue.
pmap->pm_active and pmap->pm_onproc must be destroyed.
Disabel fenv tests for arm, the implementation is incomplete.