system: fix spelling errors

Fix minor spelling errors that exists in system/Config.in

Signed-off-by: Ryan Barnett <rjbarnet@rockwellcollins.com>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Acked-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>