MLK-14982-1 imx8: lpi2c: add ipg clk for lpi2c driver

The lpi2c IP needs two clks: ipg clk and per clk. The old lpi2c
driver missed ipg clk. This patch adds ipg clk for lpi2c driver.

Signed-off-by: Gao Pan <pandy.gao@nxp.com>