build: eliminate cmake warnings

Signed-off-by: 徐宪辉 <xhxu@listenai.com>

drivers/wifi/CMakeLists.txt

 # SPDX-License-Identifier: Apache-2.0
 
-zephyr_library()
+zephyr_library_amend()
 add_subdirectory_ifdef(CONFIG_WIFI_CSK6      csk6)

modules/mbedtls/CMakeLists.txt

 if (CONFIG_MBEDTLS_BUILTIN)
 
+if (CONFIG_CSK_MBEDTLS_HARDWARE_ALT)
+
 zephyr_library()
 
 set(MBEDPATH ${ZEPHYR_BASE}/../modules/crypto/mbedtls/include)
-
-if (CONFIG_CSK_MBEDTLS_HARDWARE_ALT)
   zephyr_library_include_directories(${MBEDPATH})
   zephyr_include_directories_ifdef(CONFIG_CSK_MBEDTLS_HARDWARE_AES
     csk/csk_aes