boot: Call flush() before booting

In a lot of cases kernel resets UART HW. To ensure that U-Boot messages
printed before booting the kernel are not lost, call new U-Boot console
flush() function.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/boot/bootm_os.c b/boot/bootm_os.c
index f31820c..079224c 100644
--- a/boot/bootm_os.c
+++ b/boot/bootm_os.c
@@ -303,6 +303,7 @@
 #else
 	printf("## Starting vxWorks at 0x%08lx\n", (ulong)images->ep);
 #endif
+	flush();
 
 	boot_jump_vxworks(images);
 
diff --git a/cmd/boot.c b/cmd/boot.c
index be67a59..14839c1 100644
--- a/cmd/boot.c
+++ b/cmd/boot.c
@@ -32,6 +32,7 @@
 	addr = hextoul(argv[1], NULL);
 
 	printf ("## Starting application at 0x%08lX ...\n", addr);
+	flush();
 
 	/*
 	 * pass address parameter as argv[0] (aka command name),
diff --git a/cmd/elf.c b/cmd/elf.c
index ce40d3f..b7b9f50 100644
--- a/cmd/elf.c
+++ b/cmd/elf.c
@@ -72,6 +72,7 @@
 		return rcode;
 
 	printf("## Starting application at 0x%08lx ...\n", addr);
+	flush();
 
 	/*
 	 * pass address parameter as argv[0] (aka command name),
@@ -274,6 +275,7 @@
 		puts("## Not an ELF image, assuming binary\n");
 
 	printf("## Starting vxWorks at 0x%08lx ...\n", addr);
+	flush();
 
 	dcache_disable();
 #if defined(CONFIG_ARM64) && defined(CONFIG_ARMV8_PSCI)