r8169: enable cfg9346 config register access in atomic context

For disabling ASPM during NAPI poll we'll have to unlock access
to the config registers in atomic context. Other code parts
running with config register access unlocked are partially
longer and can sleep. Add a usage counter to enable parallel
execution of code parts requiring unlocked config registers.

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>