intel_rdt plugin: const correctness

intel_rdt plugin: const correctness

  CC       src/intel_rdt_la-intel_rdt.lo
src/intel_rdt.c: In function ‘rdt_read’:
src/intel_rdt.c:407:39: warning: passing argument 2 of ‘rdt_submit_derive’ discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
       rdt_submit_derive(cgroup->desc, "memory_bandwidth", "local",
                                       ^~~~~~~~~~~~~~~~~~
src/intel_rdt.c:339:51: note: expected ‘char *’ but argument is of type ‘const char *’
 static void rdt_submit_derive(char *cgroup, char *type, char *type_instance,
                                             ~~~~~~^~~~
src/intel_rdt.c:407:59: warning: passing argument 3 of ‘rdt_submit_derive’ discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
       rdt_submit_derive(cgroup->desc, "memory_bandwidth", "local",
                                                           ^~~~~~~
src/intel_rdt.c:339:63: note: expected ‘char *’ but argument is of type ‘const char *’
 static void rdt_submit_derive(char *cgroup, char *type, char *type_instance,
                                                         ~~~~~~^~~~~~~~~~~~~
src/intel_rdt.c:409:39: warning: passing argument 2 of ‘rdt_submit_derive’ discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
       rdt_submit_derive(cgroup->desc, "memory_bandwidth", "remote",
                                       ^~~~~~~~~~~~~~~~~~
src/intel_rdt.c:339:51: note: expected ‘char *’ but argument is of type ‘const char *’
 static void rdt_submit_derive(char *cgroup, char *type, char *type_instance,
                                             ~~~~~~^~~~
src/intel_rdt.c:409:59: warning: passing argument 3 of ‘rdt_submit_derive’ discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
       rdt_submit_derive(cgroup->desc, "memory_bandwidth", "remote",
                                                           ^~~~~~~~
src/intel_rdt.c:339:63: note: expected ‘char *’ but argument is of type ‘const char *’
 static void rdt_submit_derive(char *cgroup, char *type, char *type_instance,
                                                         ~~~~~~^~~~~~~~~~~~~