Makefile: Provide numeric versions

For SMBIOS we want to store the numeric version numbers in the tables. It
does not make sense to parse the strings. Instead, add new #defines with
the version and patchlevel.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/doc/develop/version.rst b/doc/develop/version.rst
index 6da31a4..a7797db 100644
--- a/doc/develop/version.rst
+++ b/doc/develop/version.rst
@@ -69,6 +69,14 @@
          U-Boot 2020.10 (Jan 06 2021 - 08:50:36 -0700)
          U-Boot 2021.01-rc5-00248-g60dd854f3ba-dirty (Jan 06 2021 - 08:50:36 -0700) for spring
 
+   U_BOOT_VERSION_NUM (integer #define)
+      Release year, e.g. 2021 for release 2021.01. Note
+      this is an integer, not a string.
+
+   U_BOOT_VERSION_NUM_PATCH (integer #define)
+      Patch number, e.g. 1 for release 2020.01. Note
+      this is an integer, not a string.
+
 Build date/time is also included. See the generated file
 include/generated/timestamp_autogenerated.h for the available
 fields. For example::