console: Refactor stdio_print_current_devices() a little bit

In preparation to future changes, refactor this routine a little bit.

Signed-off-by: Bin Meng <bmeng@tinylab.org>
diff --git a/common/console.c b/common/console.c
index d0640ba..af52897 100644
--- a/common/console.c
+++ b/common/console.c
@@ -1012,27 +1012,27 @@
 
 static void stdio_print_current_devices(void)
 {
+	char *stdinname, *stdoutname, *stderrname;
+
+	stdinname = stdio_devices[stdin] ?
+		    stdio_devices[stdin]->name :
+		    "No input devices available!";
+	stdoutname = stdio_devices[stdout] ?
+		     stdio_devices[stdout]->name :
+		     "No output devices available!";
+	stderrname = stdio_devices[stderr] ?
+		     stdio_devices[stderr]->name :
+		     "No error devices available!";
+
 	/* Print information */
 	puts("In:    ");
-	if (stdio_devices[stdin] == NULL) {
-		puts("No input devices available!\n");
-	} else {
-		printf ("%s\n", stdio_devices[stdin]->name);
-	}
+	printf("%s\n", stdinname);
 
 	puts("Out:   ");
-	if (stdio_devices[stdout] == NULL) {
-		puts("No output devices available!\n");
-	} else {
-		printf ("%s\n", stdio_devices[stdout]->name);
-	}
+	printf("%s\n", stdoutname);
 
 	puts("Err:   ");
-	if (stdio_devices[stderr] == NULL) {
-		puts("No error devices available!\n");
-	} else {
-		printf ("%s\n", stdio_devices[stderr]->name);
-	}
+	printf("%s\n", stderrname);
 }
 
 #if CONFIG_IS_ENABLED(SYS_CONSOLE_IS_IN_ENV)