arm64: dts: imx8-ss-dma: add IPG clock for i2c

i.MX8 LPI2C requires both PER and IPG clock, so add the missed IPG clk.

Reviewed-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>