doc: move timeutil to kernel

Move this section under the kernel and alongside other core and low
level features that are tied to the kernel.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>
diff --git a/doc/kernel/index.rst b/doc/kernel/index.rst
index 30db3c3..8c52a95 100644
--- a/doc/kernel/index.rst
+++ b/doc/kernel/index.rst
@@ -12,4 +12,5 @@
    memory_management/index.rst
    data_structures/index.rst
    timing_functions/index.rst
+   timeutil.rst
    util/index.rst
diff --git a/doc/reference/misc/timeutil.rst b/doc/kernel/timeutil.rst
similarity index 100%
rename from doc/reference/misc/timeutil.rst
rename to doc/kernel/timeutil.rst
diff --git a/doc/reference/index.rst b/doc/reference/index.rst
index b346e98..51269b2 100644
--- a/doc/reference/index.rst
+++ b/doc/reference/index.rst
@@ -31,7 +31,6 @@
    shell/index.rst
    storage/index.rst
    task_wdt/index.rst
-   misc/timeutil.rst
    usb/index.rst
    settings/index.rst
    virtualization/index.rst