clk: imx6ull: Add epdc_podf instead of sim_podf

This is one of the differences between 6ul and 6ull: imx6ull has no sim
but has epdc and this clock is redefined on the same bit.

This can be verified in the Reference Manuals.

Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>