The reset delays used for stmmac are in the order of 10ms to 1 second,
which is far too long for udelay usage, so switch to using msleep.

Practically this fixes the PHY not being reliably detected in some cases
as udelay wouldn't actually delay for long enough to let the phy
reliably be reset.
Signed-off-by: Sjoerd Simons <sjoerd.simons@collabora.co.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>