MAINTAINERS: Add an entry for AF8133J driver

As I am submitting the driver and have the device to test. I'll maintain
the driver.

Signed-off-by: Ondrej Jirman <megi@xff.cz>
Link: https://lore.kernel.org/r/20240222011341.3232645-5-megi@xff.cz
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

MAINTAINERS

@@ -579,6 +579,12 @@ F:	drivers/iio/accel/adxl372.c
 F:	drivers/iio/accel/adxl372_i2c.c
 F:	drivers/iio/accel/adxl372_spi.c
 
+AF8133J THREE-AXIS MAGNETOMETER DRIVER
+M:	Ondřej Jirman <megi@xff.cz>
+S:	Maintained
+F:	Documentation/devicetree/bindings/iio/magnetometer/voltafield,af8133j.yaml
+F:	drivers/iio/magnetometer/af8133j.c
+
 AF9013 MEDIA DRIVER
 L:	linux-media@vger.kernel.org
 S:	Orphan