PHY like the ks8721bl used on the edb9302 and similar evaluation boards
will initially not respond to the ep93xx_phy_read/write functions when
the MII-preamble is supressed. The supression is switched on by default
and must be switched off by clearing bit 8, see also EP93xx Users guide.
Removing the orphaned MII_SUPPRESS_PREAMBLE config option, note:
setting MII_SUPPRESS_PREAMBLE would actually enable the preamble transmission.

Signed-off-by: Alexander Kurz <akurz@blala.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>