serial: Allow serial to be absent in TPL

At present this option applies to SPL, but it should be available in TPL
also, and separately. Change to using CONFIG_IS_ENABLED(), add a new
Kconfig option and fix up hang().

Signed-off-by: Simon Glass <sjg@chromium.org>

drivers/serial/Kconfig

@@ -53,6 +53,16 @@ config SPL_SERIAL_PRESENT
 	  This option enables the full UART in SPL, so if is it disabled,
 	  the full UART driver will be omitted, thus saving space.
 
+config TPL_SERIAL_PRESENT
+	bool "Provide a serial driver in TPL"
+	depends on DM_SERIAL
+	default y
+	help
+	  In very space-constrained devices even the full UART driver is too
+	  large. In this case the debug UART can still be used in some cases.
+	  This option enables the full UART in TPL, so if is it disabled,
+	  the full UART driver will be omitted, thus saving space.
+
 # Logic to allow us to use the imply keyword to set what the default port
 # should be.  The default is otherwise 1.
 config CONS_INDEX_0

drivers/serial/serial-uclass.c

@@ -26,6 +26,7 @@ static const unsigned long baudrate_table[] = CONFIG_SYS_BAUDRATE_TABLE;
 #error "Serial is required before relocation - define CONFIG_$(SPL_)SYS_MALLOC_F_LEN to make this work"
 #endif
 
+#if CONFIG_IS_ENABLED(SERIAL_PRESENT)
 static int serial_check_stdout(const void *blob, struct udevice **devp)
 {
 	int node;
@@ -150,12 +151,15 @@ static void serial_find_console_or_panic(void)
 	panic_str("No serial driver found");
 #endif
 }
+#endif /* CONFIG_SERIAL_PRESENT */
 
 /* Called prior to relocation */
 int serial_init(void)
 {
+#if CONFIG_IS_ENABLED(SERIAL_PRESENT)
 	serial_find_console_or_panic();
 	gd->flags |= GD_FLG_SERIAL_READY;
+#endif
 
 	return 0;
 }

lib/hang.c

@@ -20,8 +20,9 @@
  */
 void hang(void)
 {
-#if !defined(CONFIG_SPL_BUILD) || (defined(CONFIG_SPL_LIBCOMMON_SUPPORT) && \
-		defined(CONFIG_SPL_SERIAL_SUPPORT))
+#if !defined(CONFIG_SPL_BUILD) || \
+		(CONFIG_IS_ENABLED(LIBCOMMON_SUPPORT) && \
+		 CONFIG_IS_ENABLED(SERIAL_SUPPORT))
 	puts("### ERROR ### Please RESET the board ###\n");
 #endif
 	bootstage_error(BOOTSTAGE_ID_NEED_RESET);