net: mdio-octeon: Drop obsolete Kconfig advice

"Y" was the right answer for MDIO_OCTEON when this option was only
available on CAVIUM_OCTEON_SOC. But now that the option is visible on
all (64-bit) systems, this piece of advice no longer makes sense. This
helper module is selected automatically by drivers which need it
anyway.
Signed-off-by: NJean Delvare <jdelvare@suse.de>
Fixes: a6d67864 ("net: mdio-octeon: Modify driver to work on both ThunderX and Octeon")
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Sunil Goutham <sgoutham@cavium.com>
Cc: Radha Mohan Chintakuntla <rchintakuntla@cavium.com>
Cc: David Daney <david.daney@cavium.com>
Cc: David S. Miller <davem@davemloft.net>
Acked-by: NDavid Daney <david.daney@cavium.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/phy/Kconfig

@@ -168,8 +168,6 @@ config MDIO_OCTEON
 	  busses. It is required by the Octeon and ThunderX ethernet device
 	  drivers.
 
-	  If in doubt, say Y.
-
 config MDIO_SUN4I
 	tristate "Allwinner sun4i MDIO interface support"
 	depends on ARCH_SUNXI