mfd: Constify properties in mfd_cell

Constify 'struct property_entry *properties' in mfd_cell.
It is always passed around as a pointer const struct.
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

include/linux/mfd/core.h

@@ -70,7 +70,7 @@ struct mfd_cell {
 	size_t			pdata_size;
 
 	/* device properties passed to the sub devices drivers */
-	struct property_entry *properties;
+	const struct property_entry *properties;
 
 	/*
 	 * Device Tree compatible string