src/console: add IS_ENABLED() around Kconfig symbol references

Some of these can be changed from #if to if(), but that will happen
in a follow-on commmit.

Change-Id: I5a674cd7a360a0dd040c859ec1f8d760d7c83364
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/20130
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

src/console/console.c

@@ -80,7 +80,7 @@ void console_write_line(uint8_t *buffer, size_t number_of_bytes)
 }
 
 
-#if CONFIG_GDB_STUB && (ENV_ROMSTAGE || ENV_RAMSTAGE)
+#if IS_ENABLED(CONFIG_GDB_STUB) && (ENV_ROMSTAGE || ENV_RAMSTAGE)
 void gdb_hw_init(void)
 {
 	__gdb_hw_init();