net: lan966x: Fix sleep in atomic context when updating MAC table

The function lan966x_mac_wait_for_completion is used to poll the status
of the MAC table using the function readx_poll_timeout. The problem with
this function is that is called also from atomic context. Therefore
update the function to use readx_poll_timeout_atomic.

Fixes: e18aba89

 ("net: lan966x: add mactable support")
Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>