net/smc: do not call dma sync for unmapped memory

The dma related ...sync_sg... functions check the link state before the
dma function is actually called. But the check in smc_link_usable()
allows links in ACTIVATING state which are not yet mapped to dma memory.
Under high load it may happen that the sync_sg functions are called for
such a link which results in an debug output like
   DMA-API: mlx5_core 0002:00:00.0: device driver tries to sync
   DMA memory it has not allocated [device address=0x0000000103370000]
   [size=65536 bytes]
To fix that introduce a helper to check for the link state ACTIVE and
use it where appropriate. And move the link state update to ACTIVATING
to the end of smcr_link_init() when most initial setup is done.

Reviewed-by: Ursula Braun <ubraun@linux.ibm.com>
Fixes: d854fcbf

 ("net/smc: add new link state and related helpers")
Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>