ARM: orion5x: make dns323 independent of PHY support

The D-Link DNS-323 machine tries to unconditionally select CONFIG_PHYLIB,
but that has other dependencies that might not necessarily be enabled,
causing random build errors.

To work around this, this patch removes the 'select' statement and
instead uses a compile-time check to skip the phy_register_fixup_for_uid()
call if PHYLIB is not available in the kernel.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Jason Cooper <jason@lakedaemon.net>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Gregory Clement <gregory.clement@free-electrons.com>
Cc: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>