iio: imu: st_lsm6dsx: remove set but not used variables 'acc_sensor' and 'gyro_sensor'

iio: imu: st_lsm6dsx: remove set but not used variables 'acc_sensor' and 'gyro_sensor'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c: In function 'st_lsm6dsx_read_tagged_fifo':
drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c:520:41: warning:
 variable 'gyro_sensor' set but not used [-Wunused-but-set-variable]

drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c:520:28: warning:
 variable 'acc_sensor' set but not used [-Wunused-but-set-variable]

They are not used since commit 14c7c6e1a860 ("iio: imu: st_lsm6dsx: add
st_lsm6dsx_push_tagged_data routine")

Signed-off-by: YueHaibing <[email protected]>
Acked-by: Lorenzo Bianconi <[email protected]>
Signed-off-by: Jonathan Cameron <[email protected]>