net/enc28j60: section fix

Minor bugfixes to the enc28j60 driver ... wrong section marking,
indentation, and bogus use of spi_bus_type.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Acked-by: Claudio Lanconelli <lanconelli.claudio@eptar.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>