sensor: mcux_acmp: namespace driver and kconfigs

The mcux_acmp will get support by the comparator subsystem. To avoid
namespace clashes, namespace the driver, kconfigs and use the
MCUX_ACMP config solely to select the MCUX SDK driver.

Signed-off-by: Bjarki Arge Andreasen <bjarki.andreasen@nordicsemi.no>