iio: adc: mxs-lradc: fix warning when buidling on avr32

This fixes:
drivers/staging/iio/adc/mxs-lradc.c: In function 'mxs_lradc_probe':
drivers/staging/iio/adc/mxs-lradc.c:1558: warning: comparison of distinct pointer types lacks a cast
drivers/staging/iio/adc/mxs-lradc.c:1558: warning: right shift count >= width of type
drivers/staging/iio/adc/mxs-lradc.c:1558: warning: passing argument 1 of '__div64_32' from incompatible pointer type

When building on avr32.

Reported-by: Fengguang Wu <[e-mail]>
Signed-off-by: Alexandre Belloni <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/staging/iio/adc/mxs-lradc.c

···
 	struct resource *iores;
 	int ret = 0, touch_ret;
 	int i, s;
-	unsigned int scale_uv;
+	uint64_t scale_uv;
 
 	/* Allocate the IIO device. */
 	iio = devm_iio_device_alloc(dev, sizeof(*lradc));