Fix common misspellings

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
diff --git a/drivers/isdn/hardware/eicon/message.c b/drivers/isdn/hardware/eicon/message.c
index 341ef17..8c5c563 100644
--- a/drivers/isdn/hardware/eicon/message.c
+++ b/drivers/isdn/hardware/eicon/message.c
@@ -2639,7 +2639,7 @@
     }
     else
     {
-      /* local reply if assign unsuccessfull
+      /* local reply if assign unsuccessful
          or B3 protocol allows only one layer 3 connection
            and already connected
              or B2 protocol not any LAPD
@@ -8189,7 +8189,7 @@
       dlc[ 0] = 15;
       if(b2_config->length >= 8) { /* PIAFS control abilities */
         dlc[ 7] = 10; 
-        dlc[16] = 2; /* Length of PIAFS extention */
+        dlc[16] = 2; /* Length of PIAFS extension */
         dlc[17] = PIAFS_UDATA_ABILITIES; /* control (UDATA) ability */
         dlc[18] = b2_config_parms[4].info[0]; /* value */
         dlc[ 0] = 18;