[PATCH] isdn4linux: Siemens Gigaset drivers: add README

With Hansjoerg Lipp <hjlipp@web.de>

Add a README file for the Siemens Gigaset drivers to the Documentation/isdn
directory.
Signed-off-by: Hansjoerg Lipp <hjlipp@web.de>
Signed-off-by: Tilman Schmidt <tilman@imap.cc>
Cc: Karsten Keil <kkeil@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>