delay: correct timeout_init_us()

The function has to use read_cntpct_el0() to update the counter, and not
read_cntfrq_el0().

Change-Id: I9c676466e784c3122e9ffc2d87e66708797086e7
Signed-off-by: Yann Gautier <yann.gautier@st.com>
diff --git a/include/drivers/delay_timer.h b/include/drivers/delay_timer.h
index e5044cc..20a5543 100644
--- a/include/drivers/delay_timer.h
+++ b/include/drivers/delay_timer.h
@@ -36,7 +36,7 @@
 {
 	uint64_t cnt = timeout_cnt_us2cnt(us);
 
-	cnt += read_cntfrq_el0();
+	cnt += read_cntpct_el0();
 
 	return cnt;
 }