x86/resctrl: Fix kernel-doc warnings

The kernel test robot reported kernel-doc warnings here:

  monitor.c:34: warning: Cannot understand  * @rmid_free_lru    A least recently used list of free RMIDs on line 34 - I thought it was a doc line
  monitor.c:41: warning: Cannot understand  * @rmid_limbo_count     count of currently unused but (potentially) on line 41 - I thought it was a doc line
  monitor.c:50: warning: Cannot understand  * @rmid_entry - The entry in the limbo and free lists.  on line 50 - I thought it was a doc line

We don't have a syntax for documenting individual data items via
kernel-doc, so remove the "/**" kernel-doc markers and add a hyphen
for consistency.

Fixes: 6a445edc ("x86/intel_rdt/cqm: Add RDT monitoring initialization")
Fixes: 24247aee ("x86/intel_rdt/cqm: Improve limbo list processing")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20231006235132.16227-1-rdunlap@infradead.org