nfp: implement firmware flashing

Firmware flashing takes around 60s (specified to not take more than
70s). Prevent hogging the RTNL lock in this time and make use of the
longer timeout for the NSP command. The timeout is set to 2.5 * 70
seconds.

We only allow flashing the firmware from reprs or PF netdevs. VFs do not
have an app reference.

Signed-off-by: Dirk van der Merwe <dirk.vandermerwe@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>