Do spinlock initialization during davinci_emac::probe(), when
the lock is allocated, not each time it's opened.  That's the
correct place to do such work.

More significantly, fix a bug: one of the three spinlocks was
never getting initialized, preventing the system from booting
in some cases (e.g. running with lockdep).
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>