docs/manual: fix configurations listing command

Signed-off-by: Nicolas POIROT <ni.poirot@laposte.net>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
(cherry picked from commit 5c5f30cbc78661025f2d95a98ddbe68d49e54056)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

docs/manual/customize-configuration.txt

@@ -15,8 +15,8 @@ make with +make savedefconfig BR2_DEFCONFIG=<path-to-defconfig>+.
 
 The recommended place to store this defconfig is
 +configs/<boardname>_defconfig+. If you follow this recommendation, the
-configuration will be listed in +make help+ and can be set again by
-running +make <boardname>_defconfig+.
+configuration will be listed in +make list-defconfigs+ and can be set
+again by running +make <boardname>_defconfig+.
 
 Alternatively, you can copy the file to any other place and rebuild with
 +make defconfig BR2_DEFCONFIG=<path-to-defconfig-file>+.