codec: make data tables constant.

When declaring them constant, they are written on the .rodata section
instead of .data, which means that they can be mapped directly from
disk to memory.

Signed-off-by: Diego Elio Pettenò <flameeyes@flameeyes.eu>
diff --git a/src/codec/gsm660.c b/src/codec/gsm660.c
index 4fff5ff..c044a2a 100644
--- a/src/codec/gsm660.c
+++ b/src/codec/gsm660.c
@@ -32,7 +32,7 @@
 	 * applied prior to this table, as in GSM 05.03 3.1.1, to get 260
 	 * bits from a 244 bits raw EFR frame.
 	 */
-uint16_t gsm660_bitorder[260] = {
+const uint16_t gsm660_bitorder[260] = {
 	 38,  39,  40,  41,  42,  43,		/*   0 -> LTP-LAG 1: b8..b3 */
 	145, 146, 147, 148, 149, 150,		/*   6 -> LTP-LAG 3: b8..b3 */
 	 93,  94,				/*  12 -> LTP-LAG 2: b5..b4 */