pcmcia: do not lock socket driver module in pcmcia_get_socket()

Do not lock the socket driver module in pcmcia_get_socket(), as
the PCMCIA core can handle a socket module removal: In
pcmcia_unregister_socket(), we explicitely wait for the last
put_device() to succeed.

Tested-by: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>