tianocore: fix Makefile to build a custom revision or branch

Kconfig variables TIANOCORE_REVISION and TIANOCORE_REVISION_ID
do not have an effect without this fix, the build process would
checkout the hard-coded stable hash even if these variables are set.

Change-Id: I9711a370eeade3cba0a9e127deb3d96d82adc512
Signed-off-by: Gergely Kiss <mail.gery@gmail.com>
Reviewed-on: https://review.coreboot.org/22983
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Martin Roth <martinroth@google.com>
diff --git a/payloads/external/tianocore/Makefile b/payloads/external/tianocore/Makefile
index ade0be8..c942d30e 100644
--- a/payloads/external/tianocore/Makefile
+++ b/payloads/external/tianocore/Makefile
@@ -19,6 +19,7 @@
 STABLE_COMMIT_ID=315d9d08fd77db1024ccc5307823da8aaed85e2f
 TAG-$(CONFIG_TIANOCORE_MASTER)=origin/master
 TAG-$(CONFIG_TIANOCORE_STABLE)=$(STABLE_COMMIT_ID)
+TAG-$(CONFIG_TIANOCORE_REVISION)=$(CONFIG_TIANOCORE_REVISION_ID)
 
 project_name=Tianocore
 project_dir=$(CURDIR)/tianocore