of: typo fix in __of_prop_dup()

Fix a trivial typo in a comment block.
Signed-off-by: Grant Likely <grant.likely@linaro.org>

drivers/of/dynamic.c

@@ -259,7 +259,7 @@ struct property *__of_prop_dup(const struct property *prop, gfp_t allocflags)
 
 	/*
 	 * NOTE: There is no check for zero length value.
-	 * In case of a boolean property This will allocate a value
+	 * In case of a boolean property, this will allocate a value
 	 * of zero bytes. We do this to work around the use
 	 * of of_get_property() calls on boolean values.
 	 */