Sort clock definitions in platform files

[lumag]

Define and implement a sorting order for all the clocks in the platform file.

          Very nicely sorted file :upside_down_face:

Originally posted by @MarijnS95 in #24 (comment)

[konradybcio]

I propose:

1. GCC (because most blocks need to reference it, anyway)
2. by-MMIO

[lumag]

We need to define sorting order withing the CC block. Some of the platforms use clock name, other use parent_mux_val.

[konradybcio]

within the CC block, I think only parent_mux_val makes sense here