[U-Boot] Reading from an arbitrary address over MDIO no longer works

[Alex Marginean]

Hi Carlo, everyone,

I'm doing some MDIO work on a freescale/NXP platform and I bumped into
errors with this command:
=> mdio r emdio#3 5 3
Reading from bus emdio#3
"Synchronous Abort" handler, esr 0x8600000e
elr: ffffffff862b8000 lr : 000000008200cce4 (reloc)
...

mdio list does not list any PHYs currently because ethernet is using DM
and the interfaces are not probed at this time.  The PHY does exist
on the bus though.
The above scenario works with this commit reverted:
e55047ec51a662c12ed53ff543ec7cdf158b2137 cmd: mdio: Switch to generic 
helpers when accessing the registers

The current code using generic helpers only works for PHYs that have
been registered and show up in bus->phymap and crashes for arbitrary
IDs.  I find it useful to allow reading from other addresses over MDIO
too, certainly helpful for people debugging MDIO on various boards.

What's your take on this?  Could we revert the above patch, or should I
add some code handling the case when bus->phymap comes up empty and then
go to bus->read?

Thanks!
Alex