Makefile: Add U_BOOT_TZ and include in version

Define U_BOOT_TZ alongside U_BOOT_TIME and U_BOOT_DATE and use it to
include the timezone in the version output.

Acked-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Chris Packham <judge.packham@gmail.com>
diff --git a/include/version.h b/include/version.h
index d6c7cf2..777e9f6 100644
--- a/include/version.h
+++ b/include/version.h
@@ -19,7 +19,7 @@
 #endif
 
 #define U_BOOT_VERSION_STRING U_BOOT_VERSION " (" U_BOOT_DATE " - " \
-	U_BOOT_TIME ")" CONFIG_IDENT_STRING
+	U_BOOT_TIME " " U_BOOT_TZ ")" CONFIG_IDENT_STRING
 
 #ifndef __ASSEMBLY__
 extern const char version_string[];