refactor(st-ddr): add definition for timeouts and delays

Instead of using hard-coded number in DDR driver, use macros.
Modify TIMEOUT_US_1S to DDR_TIMEOUT_US_1S to align with other defines.

Signed-off-by: Yann Gautier <yann.gautier@st.com>
Change-Id: I489084132821774b0049a4a5d7fc30db24a7bb11
diff --git a/drivers/st/ddr/stm32mp_ddr.c b/drivers/st/ddr/stm32mp_ddr.c
index 2136c71..620aa04 100644
--- a/drivers/st/ddr/stm32mp_ddr.c
+++ b/drivers/st/ddr/stm32mp_ddr.c
@@ -65,7 +65,7 @@
 	VERBOSE("[0x%lx] swctl = 0x%x\n",
 		(uintptr_t)&ctl->swctl, mmio_read_32((uintptr_t)&ctl->swctl));
 
-	timeout = timeout_init_us(TIMEOUT_US_1S);
+	timeout = timeout_init_us(DDR_TIMEOUT_US_1S);
 	do {
 		swstat = mmio_read_32((uintptr_t)&ctl->swstat);
 		VERBOSE("[0x%lx] swstat = 0x%x ",