gsm0808: fix doxygen apidoc

The api documentation names a parametery by a different name than it is
listed in the parameter list of the function. Lets make the apidoc
coherent.

Change-Id: Id21ed1e920fb64522a734f206efbe2871ec05b06
diff --git a/src/gsm/gsm0808.c b/src/gsm/gsm0808.c
index 9a9f70e..ad90008 100644
--- a/src/gsm/gsm0808.c
+++ b/src/gsm/gsm0808.c
@@ -265,7 +265,7 @@
 }
 
 /*! Create BSSMAP Cipher Mode Reject message
- *  \param[in] reason TS 08.08 cause value
+ *  \param[in] cause TS 08.08 cause value
  *  \returns callee-allocated msgb with BSSMAP Cipher Mode Reject message */
 struct msgb *gsm0808_create_cipher_reject(uint8_t cause)
 {