*: fix typo for separate(d|) in text

seperate is a common misspelling of separate

Fix all the typos in the tree that are not related to patch files.

CHANGES
  seperate -> separate, in the list of changes
Config.in.legacy
  seperate -> separate, in option name and help texts
package/leafnode2/leafnode2.mk
  seperate -> separate, in a comment
system/Config.in
  seperated -> separated, in a help text

Cc: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Ricardo Martincoski <ricardo.martincoski@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>