iio: chemical: add Atlas pH-SM sensor support

Add support for the Atlas Scientific pH-SM chemical sensor that can
detect pH levels of solutions in the range of 0-14.

Signed-off-by: Matt Ranostay <mranostay@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
diff --git a/drivers/iio/chemical/Makefile b/drivers/iio/chemical/Makefile
index 167861f..b02202b 100644
--- a/drivers/iio/chemical/Makefile
+++ b/drivers/iio/chemical/Makefile
@@ -3,5 +3,6 @@
 #
 
 # When adding new entries keep the list in alphabetical order
+obj-$(CONFIG_ATLAS_PH_SENSOR)	+= atlas-ph-sensor.o
 obj-$(CONFIG_IAQCORE)		+= ams-iaq-core.o
 obj-$(CONFIG_VZ89X)		+= vz89x.o