tests/net: Switch k_msleep to k_yield for tcp packet scheduling

TCP work queue is of higher priority so k_yield should do the trick, and
the test will not be affected by any timing.

Signed-off-by: Tomasz Bursztyka <tomasz.bursztyka@linux.intel.com>
diff --git a/tests/net/tcp2/src/main.c b/tests/net/tcp2/src/main.c
index 7253eba..183da82 100644
--- a/tests/net/tcp2/src/main.c
+++ b/tests/net/tcp2/src/main.c
@@ -1394,7 +1394,7 @@
 	zassert_true(ret == 0, "recv data failed (%d)", ret);
 
 	/* Let the IP stack to process the packet properly */
-	k_msleep(1);
+	k_yield();
 
 	/* Then we send a packet that is after the previous packet */
 	seq += 10;
@@ -1406,7 +1406,7 @@
 	ret = net_recv_data(iface, pkt);
 	zassert_true(ret == 0, "recv data failed (%d)", ret);
 
-	k_msleep(1);
+	k_yield();
 
 	/* Then send packets that are before the first packet. The final packet
 	 * will flush the receive queue as the seq will be 1
@@ -1422,7 +1422,7 @@
 		ret = net_recv_data(iface, pkt);
 		zassert_true(ret == 0, "recv data failed (%d)", ret);
 
-		k_msleep(1);
+		k_yield();
 	}
 
 	/* Then the final packet that will flush the receive queue */