sfc: Change MAC promiscuity and multicast hash at the same time

From: Steve Hodgson <shodgson@solarflare.com>

Currently we can set multicast hash immediately (in atomic context)
but must delay setting MAC promiscuity.  There is not that much
point in deferring one but not the other, and setting the multicast
hash on Siena will involve a firmware request.  So process them
both in efx_mac_work().

Also, set the broadcast bit in the multicast hash in
efx_set_multicast_list(), since this is required for both Falcon and
Siena.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>