ISDN: Make isdnhdlc usable for other ISDN drivers

isdnhdlc is useful for other ISDN drivers as well.
Move the include file to a central location and the source
to the central isdn location.

Signed-off-by: Karsten Keil <keil@b1-systems.de>
diff --git a/drivers/isdn/i4l/Kconfig b/drivers/isdn/i4l/Kconfig
index ed3510f..dd744ff 100644
--- a/drivers/isdn/i4l/Kconfig
+++ b/drivers/isdn/i4l/Kconfig
@@ -2,6 +2,8 @@
 # Old ISDN4Linux config
 #
 
+if ISDN_I4L
+
 config ISDN_PPP
 	bool "Support synchronous PPP"
 	depends on INET
@@ -135,3 +137,12 @@
 source "drivers/isdn/hysdn/Kconfig"
 
 endmenu
+# end ISDN_I4L
+endif
+
+config ISDN_HDLC
+	tristate 
+	depends on HISAX_ST5481
+	select CRC_CCITT
+	select BITREVERSE
+