all: Add 'U' suffix when using unsigned variables

Add a 'U' suffix to values when computing and comparing against
unsigned variables.

Signed-off-by: Patrik Flykt <patrik.flykt@intel.com>
diff --git a/kernel/init.c b/kernel/init.c
index b33af62..c43c904 100644
--- a/kernel/init.c
+++ b/kernel/init.c
@@ -295,7 +295,7 @@
 static void init_idle_thread(struct k_thread *thr, k_thread_stack_t *stack)
 {
 #ifdef CONFIG_SMP
-	thr->base.is_idle = 1;
+	thr->base.is_idle = 1U;
 #endif
 
 	z_setup_new_thread(thr, stack,
@@ -341,8 +341,8 @@
 	dummy_thread->base.user_options = K_ESSENTIAL;
 	dummy_thread->base.thread_state = _THREAD_DUMMY;
 #ifdef CONFIG_THREAD_STACK_INFO
-	dummy_thread->stack_info.start = 0;
-	dummy_thread->stack_info.size = 0;
+	dummy_thread->stack_info.start = 0U;
+	dummy_thread->stack_info.size = 0U;
 #endif
 #ifdef CONFIG_USERSPACE
 	dummy_thread->mem_domain_info.mem_domain = 0;