console: add console_flush_stdin()

Add a common helper console_flush_stdin() to drain all pending
characters from stdin. This consolidates the open-coded
while (tstc()) getchar() pattern that appeared in multiple places
across the tree.

Signed-off-by: Gregor Herburger <gregor.herburger@linutronix.de>
Reviewed-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>
Reviewed-by: Simon Glass <sjg@chromium.org>

cmd/conitrace.c

@@ -6,6 +6,7 @@
  * Copyright (c) 2018, Heinrich Schuchardt <xypron.glpk@gmx.de>
  */
 #include <command.h>
+#include <console.h>
 #include <linux/delay.h>
 
 static int do_conitrace(struct cmd_tbl *cmdtp, int flag, int argc,
@@ -17,8 +18,7 @@ static int do_conitrace(struct cmd_tbl *cmdtp, int flag, int argc,
 	printf("To terminate type 'x'\n");
 
 	/* Empty input buffer */
-	while (tstc())
-		getchar();
+	console_flush_stdin();
 
 	for (;;) {
 		int c = getchar();

cmd/eficonfig.c

@@ -6,8 +6,9 @@
  */
 
 #include <ansi.h>
-#include <cli.h>
 #include <charset.h>
+#include <cli.h>
+#include <console.h>
 #include <efi_device_path.h>
 #include <efi_loader.h>
 #include <efi_load_initrd.h>
@@ -167,8 +168,7 @@ static void eficonfig_menu_adjust(struct efimenu *efi_menu, bool add)
 void eficonfig_print_msg(char *msg)
 {
 	/* Flush input */
-	while (tstc())
-		getchar();
+	console_flush_stdin();
 
 	printf(ANSI_CURSOR_HIDE
 	       ANSI_CLEAR_CONSOLE

cmd/eficonfig_sbkey.c

@@ -7,6 +7,7 @@
 
 #include <ansi.h>
 #include <charset.h>
+#include <console.h>
 #include <hexdump.h>
 #include <log.h>
 #include <malloc.h>
@@ -288,8 +289,7 @@ static efi_status_t eficonfig_process_show_siglist(void *data)
 		}
 	}
 
-	while (tstc())
-		getchar();
+	console_flush_stdin();
 
 	printf("\n\n  Press any key to continue");
 	getchar();