net: phy: dp83867: perform soft reset and retain established link

Current logic is performing hard reset and causing the programmed
registers to be wiped out.

as per datasheet: https://www.ti.com/lit/ds/symlink/dp83867cr.pdf
8.6.26 Control Register (CTRL)

do SW_RESTART to perform a reset not including the registers,
If performed when link is already present,
it will drop the link and trigger re-auto negotiation.

Signed-off-by: Praneeth Bajjuri <[e-mail]>
Signed-off-by: Geet Modi <[e-mail]>
Reviewed-by: Andrew Lunn <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/phy/dp83867.c

···
 {
 	int err;
 
-	err = phy_write(phydev, DP83867_CTRL, DP83867_SW_RESET);
+	err = phy_write(phydev, DP83867_CTRL, DP83867_SW_RESTART);
 	if (err < 0)
 		return err;
 
 	usleep_range(10, 20);
 
-	/* After reset FORCE_LINK_GOOD bit is set. Although the
-	 * default value should be unset. Disable FORCE_LINK_GOOD
-	 * for the phy to work properly.
-	 */
 	return phy_modify(phydev, MII_DP83867_PHYCTRL,
 			 DP83867_PHYCR_FORCE_LINK_GOOD, 0);
 }