Support LQR controllers of various sizes

Previously, we required there to be 2 inputs and 4 states.  Lets fix
that.

Change-Id: I9a69c365a3d2bb4eb3e8b85b619ac013197cd667
diff --git a/frc971/control_loops/dlqr.h b/frc971/control_loops/dlqr.h
index 98dccb2..d169753 100644
--- a/frc971/control_loops/dlqr.h
+++ b/frc971/control_loops/dlqr.h
@@ -57,8 +57,8 @@
   // Stable eigenvalues first in the sort order
   char SORT = 'S';
 
-  long N = 4;
-  long M = 2;
+  long N = kN;
+  long M = kM;
   // Not needed since FACT = N
   long P = 0;