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

stable inclusion
from stable-5.10.47
commit 47c07f919fabb6fc8b3c27ad985f24648f5fd6df
bugzilla: 172973 https://gitee.com/openeuler/kernel/issues/I4DAKB

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=47c07f919fabb6fc8b3c27ad985f24648f5fd6df

--------------------------------

[ Upstream commit da9ef50f ]

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 <praneeth@ti.com>
Signed-off-by: Geet Modi <geet.modi@ti.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Acked-by: Weilong Chen <chenweilong@huawei.com>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>