amt: fix typo in comment

Correct spelling on 'non-existent' in comment

Signed-off-by: Ruffalo Lavoisier <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/amt.c

···
 	dev_put(amt->dev);
 }
 
-/* Non-existant group is created as INCLUDE {empty}:
+/* Non-existent group is created as INCLUDE {empty}:
  *
  * RFC 3376 - 5.1. Action on Change of Interface State
  *