Add comments describing how REG_RXFLTMAP0, REG_RXFLTMAP1 and REG_RXFLTMAP2
work.
Signed-off-by: Bruno Randolf <br1@einfach.org>
Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>