net: phy: smsc: LAN8740: add PHY_RST_AFTER_CLK_EN flag

The LAN8740, like the 8720, also requires a reset after enabling clock.
The datasheet [1] 3.8.5.1 says:
"During a Hardware reset, an external clock must be supplied
to the XTAL1/CLKIN signal."

I have observed this issue on a custom i.MX6 based board with
the LAN8740A.

[1] http://ww1.microchip.com/downloads/en/DeviceDoc/8740a.pdf

Signed-off-by: Martin Fuzzey <[e-mail]>
Reviewed-by: Andrew Lunn <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/phy/smsc.c

···
 	.name		= "SMSC LAN8740",
 
 	/* PHY_BASIC_FEATURES */
+	.flags		= PHY_RST_AFTER_CLK_EN,
 
 	.probe		= smsc_phy_probe,