net: phy: marvell: add sleep time after enabling the loopback bit

net: phy: marvell: add sleep time after enabling the loopback bit

commit 18c532e44939caa17f1fa380f7ac50dbc0718dbb upstream.

Sleep time is added to ensure the phy to be ready after loopback
bit was set. This to prevent the phy loopback test from failing.

Fixes: 020a45aff119 ("net: phy: marvell: add Marvell specific PHY loopback")
Cc: <stable@vger.kernel.org> # 5.15.x
Signed-off-by: Muhammad Husaini Zulkifli <muhammad.husaini.zulkifli@intel.com>
Signed-off-by: Aminuddin Jamaluddin <aminuddin.jamaluddin@intel.com>
Link: https://lore.kernel.org/r/20221114065302.10625-1-aminuddin.jamaluddin@intel.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>