Add timeout polling wait for auxiliary timestamps snapshot FIFO clear bit
(ATSFC) to clear. This is to ensure no residue fifo value is being read
erroneously.

Fixes: f4da5652 ("net: stmmac: Add support for external trigger timestamping")
Cc: <stable@vger.kernel.org> # 5.10.x
Signed-off-by: NNoor Azura Ahmad Tarmizi <noor.azura.ahmad.tarmizi@intel.com>
Link: https://lore.kernel.org/r/20230111050200.2130-1-noor.azura.ahmad.tarmizi@intel.comSigned-off-by: NJakub Kicinski <kuba@kernel.org>