Blackfin: fix timer_init()/timer_reset()

The timer_init() function was not using the right csync instruction, nor
was it doing it right after disabling the core timer.

The timer_reset() function would reset the timestamp, but not the actual
timer, so there was a common edge case where get_timer() return a jump of
one timestamp (couple milliseconds) right after resetting.  This caused
many functions to improperly timeout right away.

Signed-off-by: Graf Yang <graf.yang@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/cpu/blackfin/interrupts.c b/cpu/blackfin/interrupts.c
index d4dd636..bf6fb4b 100644
--- a/cpu/blackfin/interrupts.c
+++ b/cpu/blackfin/interrupts.c
@@ -95,11 +95,12 @@
 int timer_init(void)
 {
 	*pTCNTL = 0x1;
+	CSYNC();
 	*pTSCALE = 0x0;
 	*pTCOUNT = MAX_TIM_LOAD;
 	*pTPERIOD = MAX_TIM_LOAD;
 	*pTCNTL = 0x7;
-	asm("CSYNC;");
+	CSYNC();
 
 	timestamp = 0;
 	last_time = 0;
@@ -151,5 +152,5 @@
 
 void reset_timer(void)
 {
-	timestamp = 0;
+	timer_init();
 }