[PATCH] pcmcia: missing pcmcia_get_socket() result check

The result of pcmcia_get_socket() may be NULL but ds_event() uses it
without checking.

Coverity CID: 436.

Signed-off-by: Florin Malita <fmalita@gmail.com>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>