Fix common misspellings

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
diff --git a/drivers/net/wireless/atmel_cs.c b/drivers/net/wireless/atmel_cs.c
index c96e19d..0526351 100644
--- a/drivers/net/wireless/atmel_cs.c
+++ b/drivers/net/wireless/atmel_cs.c
@@ -99,7 +99,7 @@
 }
 
 /* Call-back function to interrogate PCMCIA-specific information
-   about the current existance of the card */
+   about the current existence of the card */
 static int card_present(void *arg)
 {
 	struct pcmcia_device *link = (struct pcmcia_device *)arg;