ARM: dts: r7s72100: fix ethernet clock parent

Technically, the Ethernet block is run off the 133MHz Bus (B) clock, not
the 33MHz Peripheral 0 (P0) clock.

Fixes: 969244f9 ("ARM: dts: r7s72100: add ethernet clock to device tree")
Signed-off-by: Chris Brandt <chris.brandt@renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>