iio: adc: mcp3911: fix sizeof() vs ARRAY_SIZE() bug

This code uses sizeof() instead of ARRAY_SIZE() so it reads beyond the
end of the mcp3911_osr_table[] array.

Fixes: 6d965885 ("iio: adc: mcp3911: add support for oversampling ratio")
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: NMarcus Folkesson <marcus.folkesson@gmail.com>
Link: https://lore.kernel.org/r/YzFsjY3xLHUQMjVr@kiliSigned-off-by: NJonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/mcp3911.c

@@ -248,7 +248,7 @@ static int mcp3911_write_raw(struct iio_dev *indio_dev,
 		break;
 
 	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
-		for (int i = 0; i < sizeof(mcp3911_osr_table); i++) {
+		for (int i = 0; i < ARRAY_SIZE(mcp3911_osr_table); i++) {
 			if (val == mcp3911_osr_table[i]) {
 				val = FIELD_PREP(MCP3911_CONFIG_OSR, i);
 				ret = mcp3911_update(adc, MCP3911_REG_CONFIG, MCP3911_CONFIG_OSR,