net: phy: qcom: detach qca808x PHY driver from at803x

Almost all the QCA8081 PHY driver OPs are specific and only some of them
use the generic at803x.

To make the at803x code slimmer, move all the specific qca808x regs and
functions to a dedicated PHY driver.

Probe function and priv struct is reworked to allocate and use only the
qca808x specific data. Unused data from at803x PHY driver are dropped
from at803x priv struct.

Also a new Kconfig is introduced QCA808X_PHY, to compile the newly
introduced PHY driver for QCA8081 PHY.

As the Kconfig name starts with Qualcomm the same order is kept.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20240129141600.2592-6-ansuelsmth@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>