ARM: shmobile: lager: fixup IIC2 clock frequency

Current Lager IIC2 is using default clock frequency,
but, ak4643 audio codec chip needs 100kHz
This patch clarifies IIC2 clock frequency as 100kHz.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>