iio: st_sensors: Create extended attr macro

Extend ST_SENSORS_LSM_CHANNELS() to a version that will accept extended
attributes named ST_SENSORS_LSM_CHANNELS_EXT() and wrap the former as a
specialized version of the former.

Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Denis Ciocca <denis.ciocca@st.com>
Cc: Daniel Drake <drake@endlessm.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20210518230722.522446-1-linus.walleij@linaro.orgSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

include/linux/iio/common/st_sensors.h

@@ -48,8 +48,8 @@
 #define ST_SENSORS_MAX_NAME			17
 #define ST_SENSORS_MAX_4WAI			8
 
-#define ST_SENSORS_LSM_CHANNELS(device_type, mask, index, mod, \
-					ch2, s, endian, rbits, sbits, addr) \
+#define ST_SENSORS_LSM_CHANNELS_EXT(device_type, mask, index, mod, \
+				    ch2, s, endian, rbits, sbits, addr, ext) \
 { \
 	.type = device_type, \
 	.modified = mod, \
@@ -65,8 +65,14 @@
 		.storagebits = sbits, \
 		.endianness = endian, \
 	}, \
+	.ext_info = ext, \
 }
 
+#define ST_SENSORS_LSM_CHANNELS(device_type, mask, index, mod, \
+				ch2, s, endian, rbits, sbits, addr)	\
+	ST_SENSORS_LSM_CHANNELS_EXT(device_type, mask, index, mod,	\
+				    ch2, s, endian, rbits, sbits, addr, NULL)
+
 #define ST_SENSORS_DEV_ATTR_SAMP_FREQ_AVAIL() \
 		IIO_DEV_ATTR_SAMP_FREQ_AVAIL( \
 			st_sensors_sysfs_sampling_frequency_avail)