ENGR00285692 arm: imx: add necessary clock gates into clk tree

ENGR00285692 arm: imx: add necessary clock gates into clk tree

1. add epit1, epit2 and tzasc2 clock gate to clk tree so that
clk framework can manage these clock gates;

2. adjust ipu2_di1 clock gate registry code to follow hardware
register CG index sequence.

Signed-off-by: Anson Huang <b20788@freescale.com>