net/sonic: Quiesce SONIC before re-initializing descriptor memory

net/sonic: Quiesce SONIC before re-initializing descriptor memory

BugLink: https://bugs.launchpad.net/bugs/1861385
commit 3f4b7e6a2be982fd8820a2b54d46dd9c351db899 upstream.

Make sure the SONIC's DMA engine is idle before altering the transmit
and receive descriptors. Add a helper for this as it will be needed
again.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>