MLK-10436-03: ARM: imx: Add PRG0/1 clocks as shared gate clocks for i.MX6QP

There are two PRG engines embedded in i.MX6Q R2.
The PRG0/1 axi gate clocks are derived from the ipu1/2_podf clocks respectively.
The PRG0/1 apb gate clocks are derived from the ipg clock.
The gating control bits are shared by the PRG0/1 axi/apb gate clocks.
This patch adds the gate clocks support as shared gate clocks.

Signed-off-by: Liu Ying <Ying.Liu@freescale.com>
Signed-off-by: Bai Ping <b51503@freescale.com>