This is simple change to split implementation of nvram2env to generic (MI) & MIPS-based code:
- removed includes like "*siba*", because they are unused
- added nvram2env_mips.c file with MIPS-specific code, code moved from nvram2env.c
- added header file to shared defines/structures/function prototypes between MI and MIPS code
Also this fix allows to implement own nvram2env drivers.