cpu/stm32/kconfig: rework clock tree

This splits up the clock configs.
It allows CPU_FAM based file sourcing and also common CPU_FAMs.
The dependancies are also included in wildcards would be used for the CPU_FAM macro.
This should be much more readable.
This also takes into account the HSE speeds in order to match the make/header resolution.
Some hidden symbols were added to make sorting many CPU_SERIES dependencies easier.

cpu/stm32/Kconfig

@@ -19,6 +19,8 @@ config CPU_STM32
     # This CPU requires periph_rtc when periph_rtc_mem
     select MODULE_PERIPH_RTC if MODULE_PERIPH_RTC_MEM && HAS_PERIPH_RTC
 
+menu "STM32 configuration"
+
 # Common CPU symbol
 config CPU
     default "stm32" if CPU_STM32
@@ -39,10 +41,18 @@ config MODULE_BOOTLOADER_STM32
     depends on HAS_BOOTLOADER_STM32
     depends on TEST_KCONFIG
 
-orsource "kconfigs/Kconfig.clk"
-orsource "kconfigs/*/Kconfig"
-orsource "kconfigs/*/Kconfig.lines"
-orsource "kconfigs/*/Kconfig.models"
+
+menu "STM32 clock configuration"
+    depends on CPU_STM32
+
+rsource "kconfigs/Kconfig.clk"
+rsource "kconfigs/$(CPU_FAM)/Kconfig.clk"
+
+endmenu
+
+rsource "kconfigs/$(CPU_FAM)/Kconfig"
+rsource "kconfigs/$(CPU_FAM)/Kconfig.lines"
+rsource "kconfigs/$(CPU_FAM)/Kconfig.models"
 
 choice
     prompt "ReaDout Protection level"
@@ -72,4 +82,6 @@ rsource "vectors/Kconfig"
 
 endif # TEST_KCONFIG
 
+endmenu
+
 source "$(RIOTCPU)/cortexm_common/Kconfig"