Fix common misspellings

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
diff --git a/net/atm/br2684.c b/net/atm/br2684.c
index fce2eae..2252c20 100644
--- a/net/atm/br2684.c
+++ b/net/atm/br2684.c
@@ -509,7 +509,7 @@
 	write_lock_irq(&devs_lock);
 	net_dev = br2684_find_dev(&be.ifspec);
 	if (net_dev == NULL) {
-		pr_err("tried to attach to non-existant device\n");
+		pr_err("tried to attach to non-existent device\n");
 		err = -ENXIO;
 		goto error;
 	}