net: asix: see 802.3 spec for phy reset

From: Grant Grundler <grundler@chromium.org>

https://lkml.org/lkml/2014/11/11/947



Ben Hutchings is correct. IEEE 802.3 spec section "22.2.4.1.1 Reset" requires
up to 500ms delay. Mitigate the "max" delay by polling the phy until BCM_RESET
bit is clear.

Signed-off-by: Grant Grundler <grundler@chromium.org>
Signed-off-by: Robert Foss <robert.foss@collabora.com>
Tested-by: Robert Foss <robert.foss@collabora.com>
Signed-off-by: David S. Miller <davem@davemloft.net>