pcmcia: synclink_cs: fix prototype for mgslpc_ioctl()

The ioctl file pointer was removed in commit 6caa76
"tty: now phase out the ioctl file pointer for good".

Thus fix the prototype for mgslpc_ioctl() and eliminate below warning:
  CC [M]  drivers/char/pcmcia/synclink_cs.o
drivers/char/pcmcia/synclink_cs.c:2787: warning: initialization from incompatible pointer type

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Cc: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>