Revert "net: dsa: qca8k: cache lo and hi for mdio write"

Revert "net: dsa: qca8k: cache lo and hi for mdio write"

commit 03cb9e6d0b32b768e3d9d473c5c4ca1100877664 upstream.

This reverts commit 2481d206fae7884cd07014fd1318e63af35e99eb.

The Documentation is very confusing about the topic.
The cache logic for hi and lo is wrong and actually miss some regs to be
actually written.

What the Documentation actually intended was that it's possible to skip
writing hi OR lo if half of the reg is not needed to be written or read.

Revert the change in favor of a better and correct implementation.

Reported-by: Ronald Wahl <ronald.wahl@raritan.com>
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Cc: stable@vger.kernel.org # v5.18+
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>