cannot refer to CLK_CCC_PLL1_OUT2/3

[rary21]

I think I found a bug that CLK_CCC_PLL1_OUT2/3 cannot be used in device tree.
I made a patch for this and it works in my environment.
rary21/linux4microchip#1

I couldn't find an instruction on how to contribute to upstream (https://github.com/linux4microchip/linux).
Some patches posted in the discussions were merged into upstream,
so please feel free to merge it if the patch is correct.