This driver does not depend on netmap, and umb_input() works greatly
without netmap.
Remove the #ifdef DEV_NETMAP so that when "device netmap" is not
configured this driver can still correctly pass the inbound packets to
the net stack. Otherwise the input routine will be if_input_default()
which will silently drop all inbound packets.
PR: 263783
Reported by: Andre Albsmeier <mail@fbsd2.e4m.org>
Tested by: Andre Albsmeier <mail@fbsd2.e4m.org>