stm32mp1: correct plat_crash_console_flush()

The base address of UART peripheral should be given in R0, not in R1.
Otherwise the console_stm32_core_flush issues an assert message.
This issue was highlighted with recent changes in console flush functions.

Change-Id: Iead01986fdbbf30ad2fd9fa515a1d2b611b4e591
Signed-off-by: Yann Gautier <yann.gautier@st.com>

plat/st/stm32mp1/stm32mp1_helper.S

@@ -204,7 +204,7 @@ endfunc plat_crash_console_init
 	 * ---------------------------------------------
 	 */
 func plat_crash_console_flush
-	ldr	r1, =STM32MP_DEBUG_USART_BASE
+	ldr	r0, =STM32MP_DEBUG_USART_BASE
 	b	console_stm32_core_flush
 endfunc plat_crash_console_flush