Fix common misspellings

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
diff --git a/Documentation/ABI/testing/sysfs-class-led b/Documentation/ABI/testing/sysfs-class-led
index edff663..3646ec8 100644
--- a/Documentation/ABI/testing/sysfs-class-led
+++ b/Documentation/ABI/testing/sysfs-class-led
@@ -33,5 +33,5 @@
 Description:
 		Invert the LED on/off state. This parameter is specific to
 		gpio and backlight triggers. In case of the backlight trigger,
-		it is usefull when driving a LED which is intended to indicate
+		it is useful when driving a LED which is intended to indicate
 		a device in a standby like state.