[PATCH] Char: sx, lock boards struct

Fix race condition which may occurs when multiple cards are probed at the same
time.  Add mutex to critical sections to avoid this situation.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>