can: bcm: fix warning in bcm_connect/proc_register

commit deb507f91f1adbf64317ad24ac46c56eeccfb754 upstream.

Andrey Konovalov reported an issue with proc_register in bcm.c.
As suggested by Cong Wang this patch adds a lock_sock() protection and
a check for unsuccessful proc_create_data() in bcm_connect().

Reference: http://marc.info/?l=linux-netdev&m=147732648731237



Reported-by: Andrey Konovalov <andreyknvl@google.com>
Suggested-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Tested-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Willy Tarreau <w@1wt.eu>