iio: st_pressure: Export sampling frequency for lps25h and lps331ap

Both devices are using the same iio_chan_spec to define which settings
are exported with sysfs. Both are properly configured to set/get
sampling frequency for pressure and temperature. They also properly
export available sampling frequencies. The only missing thing is
sampling_frequency sysfs file, which allows to set/get this property
from userspace.

Add sampling frequency to iio channel info mask, so sampling_frequency
file is properly exported using sysfs.

Signed-off-by: Marcin Niestroj <m.niestroj@grinn-global.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/pressure/st_pressure_core.c

@@ -143,6 +143,7 @@ static const struct iio_chan_spec st_press_1_channels[] = {
 		},
 		.info_mask_separate =
 			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
+		.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ),
 	},
 	{
 		.type = IIO_TEMP,
@@ -158,6 +159,7 @@ static const struct iio_chan_spec st_press_1_channels[] = {
 			BIT(IIO_CHAN_INFO_RAW) |
 			BIT(IIO_CHAN_INFO_SCALE) |
 			BIT(IIO_CHAN_INFO_OFFSET),
+		.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ),
 	},
 	IIO_CHAN_SOFT_TIMESTAMP(2)
 };