Sort constants in csr generation.

Sort constants in csr generation.

Previously the order of constant output depended on Python's hashing order
which changes every run. This caused the file to change every run.

With this change the csr.h file will always be the same. This can be verified
this with the following;
```bash
 CSR=software/include/generated/csr.h
 for i in 1 2 3 4 5 6; do
   rm -f $CSR; python make.py build-headers
   cp $CSR $CSR.$i
 done
 md5sum $CSR.*
```