misc: rtsx_usb: Constify struct usb_device_id

misc: rtsx_usb: Constify struct usb_device_id

rtsx_usb_usb_ids is never modified and can therefore be made const to
allow the compiler to put it in read-only memory.

Before:
   text    data     bss     dec     hex filename
  21513    4160     128   25801    64c9 drivers/misc/cardreader/rtsx_usb.o

After:
   text    data     bss     dec     hex filename
  21673    4000     128   25801    64c9 drivers/misc/cardreader/rtsx_usb.o

Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Link: https://lore.kernel.org/r/20200610224704.27082-2-rikard.falkeborn@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>