net: phy: fixed: let fixed_phy_add always use addr 0 and remove return value

net: phy: fixed: let fixed_phy_add always use addr 0 and remove return value

We have only two users of fixed_phy_add(), both use address 0 and
ignore the return value. So simplify fixed_phy_add() accordingly.

Whilst at it, constify the fixed_phy_status configs.

Note:
fixed_phy_add() is a legacy function which shouldn't be used in new
code, as it's use may be problematic:
- No check whether a fixed phy exists already at the given address
- If fixed_phy_register() is called afterwards by any other driver,
  then it will also use phy_addr 0, because fixed_phy_add() ignores
  the ida which manages address assignment
Drivers using a fixed phy created by fixed_phy_add() in platform code,
should dynamically create a fixed phy with fixed_phy_register()
instead.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://patch.msgid.link/762700e5-a0b1-41af-aa03-929822a39475@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>