kconfig: Do not print status messages in make -s mode

Add an -s option to the various frontends and pass it when make -s is
used. Also, use $(kecho) instead of @echo in the Makefile.

Signed-off-by: Michal Marek <mmarek@suse.cz>

diff --cc scripts/kconfig/Makefile
Simple merge

diff --cc scripts/kconfig/conf.c
Simple merge

diff --cc scripts/kconfig/gconf.c
Simple merge

diff --cc scripts/kconfig/mconf.c
Simple merge

diff --cc scripts/kconfig/nconf.c
Simple merge

diff --cc scripts/kconfig/qconf.cc
Simple merge