[S390] Kconfig: use common Kconfig files for s390.

Disband drivers/s390/Kconfig, use the common Kconfig files. The s390
specific config options from drivers/s390/Kconfig are moved to the
respective common Kconfig files.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
index 7ff85ad..abcafac 100644
--- a/drivers/char/Kconfig
+++ b/drivers/char/Kconfig
@@ -1081,5 +1081,7 @@
 	depends on ISA || PCI
 	default y
 
+source "drivers/s390/char/Kconfig"
+
 endmenu