clk: imx: Introduce clk_register_gate2()

Introduce imx_clk_gate2_shared2() which is similar to the existing
imx_clk_gate2_shared() and passes CLK_OPS_PARENT_ENABLE flag, which
is useful for i.MX7 shared clocks.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>