Revert "net: mdio: fix owner field for mdio buses registered using device-tree"

This reverts commit d04dac7f.

It removes of_mdiobus_register() from the symbol list, which Android
drivers are using, and they don't care about module owners as kernel
modules are not allowed to be removed on Android systems, so revert it
to preserve the ABI.

Bug: 161946584
Change-Id: I5bb5d4261bab07c3a4eeb7a41ae09d4a41d56e7e
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>