Mixers: Disable on unreachable boards

ROMFS/px4fmu_common/mixers/bebop.main.mix

+#
+# @board px4fmu-v1 exclude
+# @board px4fmu-v2 exclude
+# @board px4fmu-v3 exclude
+# @board px4fmu-v4 exclude
+# @board px4fmu-v4pro exclude
+# @board px4fmu-v5 exclude
+# @board aerofc-v1 exclude
+#
+
 Multirotor mixer for Parrot Bebop
 =================================
 

ROMFS/px4fmu_common/mixers/zmr250.main.mix

+#
+# @board px4fmu-v1 exclude
+# @board px4fmu-v2 exclude
+#
 # R: <geometry> <roll scale> <pitch scale> <yaw scale> <deadband>
 R: 4x 7654 10000 10000 0