gsm0503_interleaving: Mark input arguments as 'const *'

The interleaving/deinterleaving functions were missing 'const'
qualifiers on their input data buffers

Change-Id: I2118c34a6353167787b23f877f1d81d60151aaf9
diff --git a/include/osmocom/coding/gsm0503_interleaving.h b/include/osmocom/coding/gsm0503_interleaving.h
index 85c7328..a5d25ed 100644
--- a/include/osmocom/coding/gsm0503_interleaving.h
+++ b/include/osmocom/coding/gsm0503_interleaving.h
@@ -11,13 +11,13 @@
  */
 
 void gsm0503_xcch_deinterleave(sbit_t *cB, const sbit_t *iB);
-void gsm0503_xcch_interleave(ubit_t *cB, ubit_t *iB);
+void gsm0503_xcch_interleave(const ubit_t *cB, ubit_t *iB);
 
-void gsm0503_tch_fr_deinterleave(sbit_t *cB, sbit_t *iB);
-void gsm0503_tch_fr_interleave(ubit_t *cB, ubit_t *iB);
+void gsm0503_tch_fr_deinterleave(sbit_t *cB, const sbit_t *iB);
+void gsm0503_tch_fr_interleave(const ubit_t *cB, ubit_t *iB);
 
-void gsm0503_tch_hr_deinterleave(sbit_t *cB, sbit_t *iB);
-void gsm0503_tch_hr_interleave(ubit_t *cB, ubit_t *iB);
+void gsm0503_tch_hr_deinterleave(sbit_t *cB, const sbit_t *iB);
+void gsm0503_tch_hr_interleave(const ubit_t *cB, ubit_t *iB);
 
 void gsm0503_mcs1_ul_deinterleave(sbit_t *hc, sbit_t *dc, const sbit_t *iB);
 void gsm0503_mcs1_ul_interleave(const ubit_t *hc,