zephyr: use REQUIRED in dt_nodelabel calls to fail early and with meaningful message

When the devicetree was missing a label, I'd get this kind of errors,
which were not very helpful:
CMake Error at workspace/zephyr/cmake/modules/extensions.cmake:3979 (message):
  dt_prop(erase_size_slot1 ...) missing required argument: PATH
Call Stack (most recent call first):
  CMakeLists.txt:496 (dt_prop)

The new error message looks like this:
CMake Error at workspace/zephyr/cmake/modules/extensions.cmake:3748 (message):
  required nodelabel not found: slot1_partition

Signed-off-by: Benedek Kupper <[email protected]>

Author: benedekkupper

boot/zephyr/CMakeLists.txt

@@ -478,7 +478,7 @@ function(dt_get_parent node)
   set(${node} "${${node}}" PARENT_SCOPE)
 endfunction()
 
-dt_nodelabel(slot0_flash NODELABEL "slot0_partition")
+dt_nodelabel(slot0_flash NODELABEL "slot0_partition" REQUIRED)
 dt_prop(slot0_size PATH "${slot0_flash}" PROPERTY "reg" INDEX 1)
 dt_get_parent(slot0_flash)
 dt_get_parent(slot0_flash)
@@ -496,7 +496,7 @@ if(CONFIG_BOOT_SWAP_USING_MOVE OR CONFIG_BOOT_SWAP_USING_OFFSET)
 endif()
 
 if(NOT CONFIG_SINGLE_APPLICATION_SLOT AND NOT CONFIG_SINGLE_APPLICATION_SLOT_RAM_LOAD)
-  dt_nodelabel(slot1_flash NODELABEL "slot1_partition")
+  dt_nodelabel(slot1_flash NODELABEL "slot1_partition" REQUIRED)
   dt_prop(slot1_size PATH "${slot1_flash}" PROPERTY "reg" INDEX 1)
   dt_get_parent(slot1_flash)
   dt_get_parent(slot1_flash)
@@ -556,12 +556,12 @@ endif()
 if(SYSBUILD)
   if(CONFIG_SINGLE_APPLICATION_SLOT OR CONFIG_BOOT_FIRMWARE_LOADER OR CONFIG_BOOT_SWAP_USING_SCRATCH OR CONFIG_BOOT_SWAP_USING_MOVE OR CONFIG_BOOT_SWAP_USING_OFFSET OR CONFIG_BOOT_UPGRADE_ONLY OR CONFIG_BOOT_DIRECT_XIP OR CONFIG_BOOT_RAM_LOAD)
     # TODO: RAM LOAD support
-    dt_nodelabel(slot0_flash NODELABEL "slot0_partition")
+    dt_nodelabel(slot0_flash NODELABEL "slot0_partition" REQUIRED)
     dt_get_parent(slot0_flash)
     dt_get_parent(slot0_flash)
 
     if(NOT CONFIG_SINGLE_APPLICATION_SLOT)
-      dt_nodelabel(slot1_flash NODELABEL "slot1_partition")
+      dt_nodelabel(slot1_flash NODELABEL "slot1_partition" REQUIRED)
       dt_get_parent(slot1_flash)
       dt_get_parent(slot1_flash)