ravb: Remove obsolete explicit clock handling for WoL

Currently, if Wake-on-LAN is enabled, the EtherAVB device's module clock
is manually kept running during system suspend, to make sure the device
stays active.

Since commit 91c719f5

 ("soc: renesas: rcar-sysc: Keep wakeup
sources active during system suspend") , this workaround is no longer
needed.  Hence remove all explicit clock handling to keep the device
active.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: David S. Miller <davem@davemloft.net>