spl: Add a size check for TPL

We have the ability to enforce a maximum size for SPL but not yet for TPL.
Add a new option for this.

Document the size check macro while we are here.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/common/spl/Kconfig b/common/spl/Kconfig
index 86d7edf..c661809 100644
--- a/common/spl/Kconfig
+++ b/common/spl/Kconfig
@@ -1232,6 +1232,14 @@
 
 if TPL
 
+config TPL_SIZE_LIMIT
+	hex "Maximum size of TPL image"
+	depends on TPL
+	default 0
+	help
+	  Specifies the maximum length of the U-Boot TPL image.
+	  If this value is zero, it is ignored.
+
 config TPL_HANDOFF
 	bool "Pass hand-off information from TPL to SPL and U-Boot proper"
 	depends on HANDOFF && TPL_BLOBLIST