net: mdiobus: use flexible sleeping for reset-delay-us

MDIO bus reset pulse width is created by using udelay()
and that function might not be optimal depending on
device tree value. By switching to the new fsleep() helper
the correct delay function is called depending on
delay length, e.g. udelay(), usleep_range() or msleep().

Signed-off-by: Bruno Thomsen <bruno.thomsen@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>