nfp: allow retreiving management FW logs on representors

Users should be able to dump the management FW logs on any
of the driver's netdevs.  Make the code only depend on the
nfp_app and share it between vNICs and representors.

Storing the dump flag is simply dropped for now, since we
only support the argument being set to 0.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>