CMakeLists: Remove webos_machine_impl_dep call

* we're not interested in different behavior for emulator or desktop build
  calling this causes WEBOS_TARGET_MACHINE_IMPL to be set to simulator
  and webOS/LegacyDefines.cmake to define TARGET_DESKTOP

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Simon Busch <morphis@gravedo.de>