Env_memory_parse: move into VM

Only possible user of that function.
While here, fix bug about NR_MEMS vs MAXMEMMAP
NR_MEMS=16 is currently less than MAXMEMMAP=40; avoid overriding

include/env.h

@@ -2,5 +2,3 @@ int env_parse(char *env, char *fmt, int field, long *param, long min,
 	long max);
 void env_panic(char *env);
 int env_prefix(char *env, char *prefix);
-int env_memory_parse(struct memory *chunks, int nchunks);
-