net: designware: eqos: mimic Linux gmac4 mdio_{read, write} ...

The code was ported over from U-Boot and has some things different than
the Kernel driver:

- It reads ->mdio_address, but the kernel driver doesn't
- It doesn't write ->mdio_data in a read, but the kernel driver does
- It has delays in addition to spinning on MII_BUSY, but the kernel driver
  doesn't

Adopt the same flow as used by the kernel.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

net: designware: eqos: enable clocks before mdio_register ...

We can't be using the MAC including the MDIO controller while the clocks
are off, but this is exactly the case when mdio_register is called and
the interface is not yet up. To allow reading the PHY id to succeed
before the interface is up, turn on the clocks as part of the
initialization in the probe.

This fixes following error at probe time:

    ERROR: <NULL>: MDIO not idle at entry

The NULL is fixed in a follow-up commit.

Signed-off-by: Ahmad Fatoum <ahmad@a3f.at>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

net: add Designware Ethernet QoS for STM32MP ...

We already have Designware NIC support in barebox, but for the DWMAC1000,
the DWMAC4 (also called GMAC4), no support was mainline so far.

The DWMAC4 is different enough that sharing code with the DWMAC1000 is
not really that helpful, because even basics like MDIO registers have
different layout. Instead of coding bit masks and shifts into the driver
data, like Linux does, we'll keep both driver kinds separate.

Nevertheless, we collect functions that are not SoC-specific into a
separate 'library' file.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>