net: aquantia: Fix a regression with reset on old firmware

FW 1.5.58 and below needs a fixed delay even after 0x18 register
is filled. Otherwise, setting MPI_INIT state too fast causes
traffic hang.

Signed-off-by: Igor Russkikh <igor.russkikh@aquantia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>