Add support for retrieving TTC configuration from device tree.  This
includes the ability to pull information about the driving clocks from
the of_clk bindings.

Signed-off-by: Josh Cartwright <redacted>
---

diff --git a/drivers/clocksource/xilinx_ttc.c b/drivers/clocksource/xilinx_ttc.c
index ff38b3e..a4718f7 100644
--- a/drivers/clocksource/xilinx_ttc.c
+++ b/drivers/clocksource/xilinx_ttc.c

@@ -209,7 +153,8 @@ static struct clocksource clocksource_xttcpss = {
 static int xttcpss_set_next_event(unsigned long cycles,
 					struct clock_event_device *evt)
 {
-	struct xttcpss_timer *timer = &timers[XTTCPSS_CLOCKEVENT];
+	struct xttcpss_timer_clockevent *xttce = to_xttcpss_timer_clkevent(evt);
+	struct xttcpss_timer *timer = &xttce->xttc;
 
 	xttcpss_set_interval(timer, cycles);
 	return 0;

@@ -224,12 +169,14 @@ static int xttcpss_set_next_event(unsigned long cycles,
 static void xttcpss_set_mode(enum clock_event_mode mode,
 					struct clock_event_device *evt)
 {
-	struct xttcpss_timer *timer = &timers[XTTCPSS_CLOCKEVENT];
+	struct xttcpss_timer_clockevent *xttce = to_xttcpss_timer_clkevent(evt);
+	struct xttcpss_timer *timer = &xttce->xttc;
 	u32 ctrl_reg;
 
 	switch (mode) {
 	case CLOCK_EVT_MODE_PERIODIC:
-		xttcpss_set_interval(timer, TIMER_RATE / HZ);
+		xttcpss_set_interval(timer,
+				     clk_get_rate(xttce->clk) / PRESCALE);