c03: fixed apidoc.

avr/devices/c03/main/a_c03.asm

@@ -489,6 +489,7 @@ C03App_OnCmdBack:
 ; @param r17 value for WIDGET_OFFS_PACK
 ; @param r21:r20 img ressource
 ; @param r22     selector
+; @param r23     button mode
 ; @return CFLAG  set if new object created, cleared on error
 ; @return Y      button created
 ; @clobbers any, !X