iio:common:meas-spec: Move exports into IIO_MEAS_SPEC_SENSORS

iio:common:meas-spec: Move exports into IIO_MEAS_SPEC_SENSORS

The obvious choice of ms_sensors felt rather too likely to clash with other
namespaces introduced in future, hence the longer abbreviation.

In order to avoid unnecessary pollution of the global symbol namespace
move the common/library functions into a specific namespace and import
that into the various specific device drivers that use them.

For more information see https://lwn.net/Articles/760045/

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: William Markezana <william.markezana@meas-spec.com>
Cc: Ludovic Tancerel <ludovic.tancerel@maplehightech.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20220130205701.334592-5-jic23@kernel.org