omnia-mcutool: fix location of mcutool.c

This package failed with following output: arm-openwrt-linux-muslgnueabi-gcc: error: /foo/build/build_dir/target-arm_cortex-a9+vfpv3-d16_musl_eabi/omnia-mcutool-0.1/mcutool/mcutool.c: No such file or directory

I found that mcutool.c is located at build_dir/target-arm_cortex-a9+vfpv3-d16_musl_eabi/omnia-mcutool-0.1/mcutool.c

So folder mcutool was reduntant and because of it, I removed it and package omnia-mcutool can be compiled.