In [0] the paper concludes with
> The Knuth LCG is the most efficient general purpose generator that
> provides decent statistical quality.
> It is simple and lean enough to run on very constrained devices.
So let's select `prng_musl_lcg` to be the default PRNG instead of
`prng_tinymt32`.
This gives a good chunk of memory on e.g. `samr21-xpro`:
prng_tinymt32
-------------
text data bss dec hex filename
26452 136 2824 29412 72e4 tests/rng/bin/samr21-xpro/tests_rng.elf
prng_musl_lcg
-------------
text data bss dec hex filename
26208 136 2808 29152 71e0 tests/rng/bin/samr21-xpro/tests_rng.elf
[0] https://sci-hub.se/10.1145/3453159
