Fix common misspellings and typos

Change-Id: I8152acaccd33a4b646d56cba0748aeefa0c16b35
diff --git a/include/osmocom/rspro/per_support.h b/include/osmocom/rspro/per_support.h
index 181fe24..ed945ce 100644
--- a/include/osmocom/rspro/per_support.h
+++ b/include/osmocom/rspro/per_support.h
@@ -53,7 +53,7 @@
  */
 int32_t per_get_few_bits(asn_per_data_t *per_data, int get_nbits);
 
-/* Undo the immediately preceeding "get_few_bits" operation */
+/* Undo the immediately preceding "get_few_bits" operation */
 void per_get_undo(asn_per_data_t *per_data, int get_nbits);
 
 /*