iio: fix spelling of subsystem

Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/Kconfig

 #
-# Industrial I/O subsytem configuration
+# Industrial I/O subsystem configuration
 #
 
 menuconfig IIO

drivers/staging/iio/Kconfig

 #
-# Industrial I/O subsytem configuration
+# Industrial I/O subsystem configuration
 #
 menu "IIO staging drivers"
 	depends on IIO