chan_dahdi: Fix insufficient array size for round robin.

According to chan_dahdi.conf, up to 64 groups (numbered
0 through 63) can be used when dialing DAHDI channels.

However, currently dialing round robin with a group number
greater than 31 fails because the array for the round robin
structure is only size 32, instead of 64 as it should be.

This fixes that so the round robin array size is consistent
with the actual groups capacity.

ASTERISK-29994

Change-Id: I4caa08d7025f78ac75a0539f71aaf3eb3e85b3b7

channels/chan_dahdi.c

@@ -3410,7 +3410,7 @@ struct analog_callback analog_callbacks =
 };
 
 /*! Round robin search locations. */
-static struct dahdi_pvt *round_robin[32];
+static struct dahdi_pvt *round_robin[64]; /* groups can range from 0-63 */
 
 int _dahdi_get_index(struct ast_channel *ast, struct dahdi_pvt *p, int nullok, const char *fname, unsigned long line)
 {