cmake: remove all module.mk files & cmake conversion script (#4918)

It seems these files are leftovers.

src/modules/systemlib/mixer/module.mk

@@ -1,47 +0,0 @@
-############################################################################
-#
-#   Copyright (c) 2012, 2013 PX4 Development Team. All rights reserved.
-#
-# Redistribution and use in source and binary forms, with or without
-# modification, are permitted provided that the following conditions
-# are met:
-#
-# 1. Redistributions of source code must retain the above copyright
-#    notice, this list of conditions and the following disclaimer.
-# 2. Redistributions in binary form must reproduce the above copyright
-#    notice, this list of conditions and the following disclaimer in
-#    the documentation and/or other materials provided with the
-#    distribution.
-# 3. Neither the name PX4 nor the names of its contributors may be
-#    used to endorse or promote products derived from this software
-#    without specific prior written permission.
-#
-# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
-# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
-# COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
-# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
-# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
-# OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
-# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
-# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
-# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
-# POSSIBILITY OF SUCH DAMAGE.
-#
-############################################################################
-
-
-#
-# mixer library
-#
-LIBNAME	= mixerlib
-	
-SRCS		= mixer.cpp \
-		  mixer_group.cpp \
-		  mixer_multirotor.cpp \
-		  mixer_simple.cpp \
-		  mixer_load.c
-
-SELF_DIR := $(dir $(lastword $(MAKEFILE_LIST)))
-include $(SELF_DIR)multi_tables.mk