ARM: mach-shmobile: clock-r8a7740: add sh-eth clock

armadillo800eva board is using sh-eth, but clock-r8a7740 didn't care it.
This clock was enabled by boot-loader.
This patch fix it up.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Reviewed-by: Simon Horman <horms@verge.net.au>
Acked-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>