dm: timer: Support 64-bit counter

There are timers with a 64-bit counter value but current timer
uclass driver assumes a 32-bit one. Modify timer_get_count()
to ask timer driver to always return a 64-bit counter value,
and provide an inline helper function timer_conv_64() to handle
the 32-bit/64-bit conversion automatically.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/timer/altera_timer.c b/drivers/timer/altera_timer.c
index 2364f1b..89fe05b 100644
--- a/drivers/timer/altera_timer.c
+++ b/drivers/timer/altera_timer.c
@@ -34,7 +34,7 @@
 	struct altera_timer_regs *regs;
 };
 
-static int altera_timer_get_count(struct udevice *dev, unsigned long *count)
+static int altera_timer_get_count(struct udevice *dev, u64 *count)
 {
 	struct altera_timer_platdata *plat = dev->platdata;
 	struct altera_timer_regs *const regs = plat->regs;
@@ -46,7 +46,7 @@
 	/* Read timer value */
 	val = readl(&regs->snapl) & 0xffff;
 	val |= (readl(&regs->snaph) & 0xffff) << 16;
-	*count = ~val;
+	*count = timer_conv_64(~val);
 
 	return 0;
 }