clk: imx7d: fix mipi dphy div parent

Fix the mipi dphy root divider to mipi_dphy_pre_div, this would remove a orphan
clock and set the correct parent.

before:
cat clk_orphan_summary
                                 enable  prepare  protect
   clock                          count    count    count        rate   accuracy   phase
----------------------------------------------------------------------------------------
 mipi_dphy_post_div                   1        1        0           0          0 0
    mipi_dphy_root_clk                1        1        0           0          0 0

cat clk_dump | grep mipi_dphy
mipi_dphy_post_div                    1        1        0           0          0 0
    mipi_dphy_root_clk                1        1        0           0          0 0

after:
cat clk_dump | grep mipi_dphy
   mipi_dphy_src                     1        1        0    24000000          0 0
       mipi_dphy_cg                  1        1        0    24000000          0 0
          mipi_dphy_pre_div          1        1        0    24000000          0 0
             mipi_dphy_post_div      1        1        0    24000000          0 0
                mipi_dphy_root_clk   1        1        0    24000000          0 0

Fixes: 8f6d8094 ("ARM: imx: add imx7d clk tree support")
Acked-by: Dong Aisheng <Aisheng.dong@nxp.com>
Signed-off-by: Rui Miguel Silva <rui.silva@linaro.org>

Signed-off-by: Stephen Boyd <sboyd@kernel.org>