gateware: Rework the low-level line state monitoring ticks

The 'tick' system was meant to allow the firmware to monitor the
low level state of the line, beyong just "not aligned", but it was
never really useful in the present state.

Now we have more tick source available (but only one can be measured
at the same time). More specifically, the firmware can monitor the
presence/absence of raw pulses (LOS condition), it can also monitor
the number of '1' pulses to detect an AIS signals, or simply the rate
of RX pulses (to tune the local oscillator to incoming signal rate).

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
Change-Id: I31fa8a717a26643f1b6ca5644bee1d8c41a2512e
diff --git a/gateware/common/rtl/soc_base.v b/gateware/common/rtl/soc_base.v
index 25c4af8..be7766a 100644
--- a/gateware/common/rtl/soc_base.v
+++ b/gateware/common/rtl/soc_base.v
@@ -72,9 +72,8 @@
 	input  wire [ WB_N    -1:0] wb_m_ack,
 
 	// Ticks
-	output wire [E1_N-1:0] tick_e1_rx,
-	output wire [E1_N-1:0] tick_e1_tx,
-	output wire            tick_usb_sof,
+	output wire [4*E1_N-1:0] tick_e1,
+	output wire              tick_usb_sof,
 
 	// Clock / Reset
 	input  wire clk_sys,
@@ -502,8 +501,7 @@
 		.wb_cyc      (wb_cyc[7]),
 		.wb_ack      (wb_ack[7]),
 		.irq         (),
-		.tick_rx     (tick_e1_rx),
-		.tick_tx     (tick_e1_tx),
+		.mon_tick    (tick_e1),
 		.clk         (clk_sys),
 		.rst         (rst_sys)
 	);