spl: Make SPL_DISABLE_BANNER_PRINT a positive option

Rather than having a negative option, make this a positive option and
enable it by default. This makes it easier to understand.

Reviewed-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/common/spl/spl.c b/common/spl/spl.c
index 23be33c..5a026b8 100644
--- a/common/spl/spl.c
+++ b/common/spl/spl.c
@@ -607,7 +607,7 @@
 
 	gd->have_console = 1;
 
-#ifndef CONFIG_SPL_DISABLE_BANNER_PRINT
+#if CONFIG_IS_ENABLED(BANNER_PRINT)
 	puts("\nU-Boot " SPL_TPL_NAME " " PLAIN_VERSION " (" U_BOOT_DATE " - "
 	     U_BOOT_TIME " " U_BOOT_TZ ")\n");
 #endif