dpif-netdev: Use compatible function type to fix broken build.

dpif-netdev: Use compatible function type to fix broken build.

The dpif_provder flow_dump_create function signature was changed, but
the netdev dpif was not updated along with it.  This generated a build
error with the following warnings:

libtool: compile:  gcc -std=gnu99 -DHAVE_CONFIG_H -I. -I ./include -I ./include -I ./lib -I ./lib -Wstrict-prototypes -Wall -Wextra -Wno-sign-compare -Wpointer-arith -Wformat -Wformat-security -Wswitch-enum -Wunused-parameter -Wbad-function-cast -Wcast-align -Wstrict-prototypes -Wold-style-definition -Wmissing-prototypes -Wmissing-field-initializers -fno-strict-aliasing -Wshadow -Wno-null-pointer-arithmetic -Werror -Werror -g -O2 -MT lib/dpif-netdev.lo -MD -MP -MF lib/.deps/dpif-netdev.Tpo -c lib/dpif-netdev.c -o lib/dpif-netdev.o
lib/dpif-netdev.c:6812:5: error: initialization from incompatible pointer type [-Werror]
     dpif_netdev_flow_dump_create,
     ^
lib/dpif-netdev.c:6812:5: error: (near initialization for 'dpif_netdev_class.flow_dump_create') [-Werror]

Fixes: ab15e70eb587 ("dpctl: Expand the flow dump type filter")
Cc: Gavi Teitz <gavi@mellanox.com>
Cc: Roi Dayan <roid@mellanox.com>
Cc: Simon Horman <simon.horman@netronome.com>
Signed-off-by: Aaron Conole <aconole@redhat.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>