r8169: use spinlock to protect access to registers Config2 and Config5

r8169: use spinlock to protect access to registers Config2 and Config5

BugLink: https://bugs.launchpad.net/bugs/1946433
For disabling ASPM during NAPI poll we'll have to access both registers
in atomic context. Use a spinlock to protect access.

Reviewed-by: Simon Horman <simon.horman@corigine.com>
Tested-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 6bc6c4e6893ee79a9862c61d1635e7da6d5a3333)
Signed-off-by: Koba Ko <koba.ko@canonical.com>
Acked-by: Andrei Gherzan <andrei.gherzan@canonical.com>
Acked-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>