tools: iio: make iioutils_get_type() private in iio_utils

tools: iio: make iioutils_get_type() private in iio_utils

This is a bit of a tidy-up, but also helps with extending the
iioutils_get_type() function a bit, as we don't need to use it outside of
the iio_utils.c file. So, we'll need to update it only in one place.

With this change, the 'unsigned' types are updated to 'unsigned int' in the
iioutils_get_type() function definition.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20210215104043.91251-23-alexandru.ardelean@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>