kconfig infra: remove all install stamp files

Some packages (like linux) may install things inside images/ as well, so
remove the associated stamp file after running the configuration editor.

Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Signed-off-by: "Yann E. Morin" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>