iio: fix scale application in iio_convert_raw_to_processed_unlocked

iio: fix scale application in iio_convert_raw_to_processed_unlocked

When the scale_type is IIO_VAL_INT_PLUS_MICRO or IIO_VAL_INT_PLUS_NANO
the scale passed as argument is only applied to the fractional part of
the value. Fix it by also multiplying the integer part by the scale
provided.

Fixes: 48e44ce0f881 ("iio:inkern: Add function to read the processed value")
Signed-off-by: Matteo Martelli <matteomartelli3@gmail.com>
Link: https://patch.msgid.link/20240730-iio-fix-scale-v1-1-6246638c8daa@gmail.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>