unify system_clock.c for STM32U5

Author: wdx04

targets/TARGET_STM/TARGET_STM32U5/CMakeLists.txt

@@ -18,6 +18,7 @@ target_include_directories(mbed-stm32u5
 
 target_sources(mbed-stm32u5
     INTERFACE
+        clock_cfg/system_clock.c
         analogin_device.c
         analogout_device.c
         flash_api.c

targets/TARGET_STM/TARGET_STM32U5/TARGET_STM32U545xE/CMakeLists.txt

@@ -21,7 +21,6 @@ target_include_directories(mbed-stm32u545xe
 target_sources(mbed-stm32u545xe
     INTERFACE
         ${STARTUP_FILE}
-        system_clock.c
 )
 
 mbed_set_linker_script(mbed-stm32u545xe ${CMAKE_CURRENT_SOURCE_DIR}/${LINKER_FILE})

targets/TARGET_STM/TARGET_STM32U5/TARGET_STM32U545xE/system_clock.c

@@ -19,7 +19,6 @@ target_include_directories(mbed-stm32u575xg
 target_sources(mbed-stm32u575xg
     INTERFACE
         ${STARTUP_FILE}
-        system_clock.c
 )
 
 mbed_set_linker_script(mbed-stm32u575xg ${CMAKE_CURRENT_SOURCE_DIR}/${LINKER_FILE})

targets/TARGET_STM/TARGET_STM32U5/TARGET_STM32U575xG/CMakeLists.txt

@@ -21,7 +21,6 @@ target_include_directories(mbed-stm32u575xi
 target_sources(mbed-stm32u575xi
     INTERFACE
         ${STARTUP_FILE}
-        system_clock.c
 )
 
 mbed_set_linker_script(mbed-stm32u575xi ${CMAKE_CURRENT_SOURCE_DIR}/${LINKER_FILE})