graphics/nxmu/nxmu_start.c: Extend nxmu_start so that receives a display number as an argument. This makes it possible to have multiple instances of the NX server running on boards that support multiple displays. Also includes updates to boardctl() to accept display number paramters.

include/nuttx/nx/nxmu.h

@@ -480,7 +480,8 @@ extern "C"
  *   boardctl() interface with the BOARDIOC_NX_START command.
  *
  * Input Parameters:
- *   None
+ *   display - Display number served by this NXMU instance.
+ *   plane   - Plane number to use for display info
  *
  * Returned Value:
  *   Zero (OK) is returned on success.  This indicates that the NX server
@@ -492,7 +493,7 @@ extern "C"
  *
  ****************************************************************************/
 
-int nxmu_start(void);
+int nxmu_start(int display, int plane);
 
 /****************************************************************************
  * Name: nxfe_constructwindow

include/sys/boardctl.h

@@ -115,7 +115,7 @@
  *
  * CMD:           BOARDIOC_NX_START
  * DESCRIPTION:   Start the NX server
- * ARG:           None
+ * ARG:           Integer display number to be served by this NXMU instance.
  * CONFIGURATION: CONFIG_NX
  * DEPENDENCIES:  Base graphics logic provides nxmu_start()
  *