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/myri_sbus.c b/drivers/net/myri_sbus.c
index a761076..53aeea4 100644
--- a/drivers/net/myri_sbus.c
+++ b/drivers/net/myri_sbus.c
@@ -1009,7 +1009,7 @@
 
 	/* Map in the MyriCOM register/localram set. */
 	if (mp->eeprom.cpuvers < CPUVERS_4_0) {
-		/* XXX Makes no sense, if control reg is non-existant this
+		/* XXX Makes no sense, if control reg is non-existent this
 		 * XXX driver cannot function at all... maybe pre-4.0 is
 		 * XXX only a valid version for PCI cards?  Ask feldy...
 		 */