doc: add missing table of content links

add missing table of content links, make alphabetical

Signed-off-by: Sam Povilus <sam.povilus@amd.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/usage/fit/index.rst b/doc/usage/fit/index.rst
index 68231e9..a822bf2 100644
--- a/doc/usage/fit/index.rst
+++ b/doc/usage/fit/index.rst
@@ -10,10 +10,23 @@
 .. toctree::
     :maxdepth: 1
 
-    source_file_format
+    beaglebone_vboot
     howto
-    x86-fit-boot
+    kernel_fdt
+    kernel_fdts_compressed
+    kernel
+    multi
+    multi_spl
+    multi-with-fpga
+    multi-with-loadables
+    overlay-fdt-boot
+    sec_firmware_ppa
     signature
+    sign-configs
+    sign-images
+    source_file_format
+    uefi
+    update3
+    update_uboot
     verified-boot
-    beaglebone_vboot
-    overlay-fdt-boot
+    x86-fit-boot
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