extdep: Removed add_dependencies call from CMakeLists

Small change to get rid of a warning in newer cmake versions.

Versions of cmake (>= 3.0) throw a warning on the add_dependecy
method for non-existant dependencies (add_dependency call before
target_link_libraries call).

Removed the call to add_dependency since target_link_libraries should
provide the same functionality for ozw and modbus dependencies.

Signed-off-by: Noel Eck <noel.eck@intel.com>

src/h803x/CMakeLists.txt

   set (reqlibname "libmodbus")
   include_directories(${MODBUS_INCLUDE_DIRS})
   upm_module_init()
-  add_dependencies(${libname} ${MODBUS_LIBRARIES})
   target_link_libraries(${libname} ${MODBUS_LIBRARIES})
   if (BUILDSWIG)
     if (BUILDSWIGNODE)

src/hwxpxx/CMakeLists.txt

   set (reqlibname "libmodbus")
   include_directories(${MODBUS_INCLUDE_DIRS})
   upm_module_init()
-  add_dependencies(${libname} ${MODBUS_LIBRARIES})
   target_link_libraries(${libname} ${MODBUS_LIBRARIES})
   if (BUILDSWIG)
     if (BUILDSWIGNODE)

src/ozw/CMakeLists.txt

   set (reqlibname "libopenzwave")
   include_directories(${OPENZWAVE_INCLUDE_DIRS})
   upm_module_init()
-  add_dependencies(${libname} ${OPENZWAVE_LIBRARIES})
   target_link_libraries(${libname} ${OPENZWAVE_LIBRARIES})
   if (BUILDSWIG)
     if (BUILDSWIGNODE)

src/t3311/CMakeLists.txt

   set (reqlibname "libmodbus")
   include_directories(${MODBUS_INCLUDE_DIRS})
   upm_module_init()
-  add_dependencies(${libname} ${MODBUS_LIBRARIES})
   target_link_libraries(${libname} ${MODBUS_LIBRARIES})
   if (BUILDSWIG)
     if (BUILDSWIGNODE)