[nrf noup] zephyr: Remove duplication from cmake

Removes the `add_subdirectory`
of nrfxlib it will still check that the nrfxlib is located outside
the mcuboot directory.

Signed-off-by: Sigvart Hovland <sigvart.m@gmail.com>
Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>
Signed-off-by: Martí Bolívar <marti.bolivar@nordicsemi.no>
Signed-off-by: Emil Obalski <emil.obalski@nordicsemi.no>
Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>
Signed-off-by: Håkon Øye Amundsen <haakon.amundsen@nordicsemi.no>
Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>
Signed-off-by: Jamie McCrae <jamie.mccrae@nordicsemi.no>
(cherry picked from commit d2c6668)

boot/zephyr/CMakeLists.txt

@@ -74,8 +74,6 @@ if(NOT EXISTS ${NRFXLIB_DIR})
  To use the tinycrypt set `CONFIG_BOOT_ECDSA_TINYCRYPT` to y.
  ------------------------------------------------------------------------")
 endif()
-# Don't include this if we are using west
- add_subdirectory(${NRFXLIB_DIR} ${PROJECT_BINARY_DIR}/nrfxlib)
 endif()
 
 zephyr_library_include_directories(