iio: accel: mma9553: fix gpio bitnum init value

Initial value of gpio bitnum is set to -1, but
the variable is declared as unsigned.

Use a positive invalid value for initial gpio
bitnum.

Signed-off-by: Irina Tirdea <[e-mail]>
Suggested-by: Hartmut Knaack <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/accel/mma9553.c

···
 
 /* Bitnum used for GPIO configuration = bit number in high status byte */
 #define MMA9553_STATUS_TO_BITNUM(bit)	(ffs(bit) - 9)
+#define MMA9553_MAX_BITNUM		MMA9553_STATUS_TO_BITNUM(BIT(16))
 
 #define MMA9553_DEFAULT_SAMPLE_RATE	30	/* Hz */
 
···
 	}
 
 
-	data->gpio_bitnum = -1;
 	/* Reset GPIO */
+	data->gpio_bitnum = MMA9553_MAX_BITNUM;
 	ret = mma9553_conf_gpio(data);
 	if (ret < 0)
 		return ret;