char/pcmcia: add some error checking in scr24x_read()

The "ret = " assignment seems to have accidentally been left off.

Fixes: f2ed287b

 ("char/pcmcia: add scr24x_cs chip card interface driver")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Lubomir Rintel <lkundrak@v3.sk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>