iio: accel: st_accel: fix LIS3LV02 reading and scaling

The LIS3LV02 has a special bit that need to be set to get the
read values left aligned. Before this patch we get gibberish
like this:

iio_generic_buffer -a -c10 -n lis3lv02dl_accel
(...)
0.000000 -0.010042 -0.642688 19155832931907
0.000000 -0.010042 -0.642688 19155858751073

Which is because we read a raw value for 1g as 64 which is
the nominal 1024 for 1g shifted 4 bits to the left by being
right-aligned rather than left aligned.

Since all other sensors are left aligned, add some code to
set the special DAS (data alignment setting) bit to 1 so that
the right value is now read like this:

iio_generic_buffer -a -c10 -n lis3lv02dl_accel
(...)
0.000000 -0.147095 -10.120135 24761614364956
-0.029419 -0.176514 -10.120135 24761631624540

The scaling was weird as well: we have a gain of 1000 for 1g
and 3000 for 6g. I don't even remember how I came up with the
old values but they are wrong.

Fixes: 3acddf74f8 ("iio: st-sensors: add support for lis3lv02d accelerometer")
Cc: Lorenzo Bianconi <lorenzo.bianconi@st.com>
Cc: Giuseppe Barba <giuseppe.barba@st.com>
Cc: Denis Ciocca <denis.ciocca@st.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/accel/st_accel_core.c

@@ -353,12 +353,12 @@ static const struct st_sensor_settings st_accel_sensors_settings[] = {
 				[0] = {
 					.num = ST_ACCEL_FS_AVL_2G,
 					.value = 0x00,
-					.gain = IIO_G_TO_M_S_2(1024),
+					.gain = IIO_G_TO_M_S_2(1000),
 				},
 				[1] = {
 					.num = ST_ACCEL_FS_AVL_6G,
 					.value = 0x01,
-					.gain = IIO_G_TO_M_S_2(340),
+					.gain = IIO_G_TO_M_S_2(3000),
 				},
 			},
 		},
@@ -366,6 +366,14 @@ static const struct st_sensor_settings st_accel_sensors_settings[] = {
 			.addr = 0x21,
 			.mask = 0x40,
 		},
+		/*
+		 * Data Alignment Setting - needs to be set to get
+		 * left-justified data like all other sensors.
+		 */
+		.das = {
+			.addr = 0x21,
+			.mask = 0x01,
+		},
 		.drdy_irq = {
 			.addr = 0x21,
 			.mask_int1 = 0x04,