P2P: Fix the calculation of group common freqs

Previously, the calculation allowed for the same frequency to appear
several times in the result.

Signed-off-by: Ilan Peer <ilan.peer@intel.com>
diff --git a/src/p2p/p2p_utils.c b/src/p2p/p2p_utils.c
index e139d03..2e2aa8a 100644
--- a/src/p2p/p2p_utils.c
+++ b/src/p2p/p2p_utils.c
@@ -459,12 +459,22 @@
 			break;
 		for (j = 0; j < c->channels; j++) {
 			int freq;
+			unsigned int k;
+
 			if (idx + 1 == max_len)
 				break;
 			freq = p2p_channel_to_freq(c->reg_class,
 						   c->channel[j]);
 			if (freq < 0)
 				continue;
+
+			for (k = 0; k < idx; k++) {
+				if (freq_list[k] == freq)
+					break;
+			}
+
+			if (k < idx)
+				continue;
 			freq_list[idx++] = freq;
 		}
 	}