staging: comedi: ni_tio_internal.h: add missing NITIO_*_REG macro

The "HW Save" registers are the only ones missing an access macro.
Add one for completness.
Signed-off-by: NH Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: NIan Abbott <abbotti@mev.co.uk>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/ni_tio_internal.h

@@ -23,6 +23,7 @@
 
 #define NITIO_AUTO_INC_REG(x)		(NITIO_G0_AUTO_INC + (x))
 #define NITIO_CMD_REG(x)		(NITIO_G0_CMD + (x))
+#define NITIO_HW_SAVE_REG(x)		(NITIO_G0_HW_SAVE + (x))
 #define NITIO_SW_SAVE_REG(x)		(NITIO_G0_SW_SAVE + (x))
 #define NITIO_MODE_REG(x)		(NITIO_G0_MODE + (x))
 #define NITIO_LOADA_REG(x)		(NITIO_G0_LOADA + (x))