tee: optee: support AVB trusted application

Adds configuration option OPTEE_TA_AVB and a header file describing the
interface to the Android Verified Boot 2.0 (AVB) trusted application
provided by OP-TEE.

Tested-by: Igor Opaniuk <igor.opaniuk@linaro.org>
Reviewed-by: Igor Opaniuk <igor.opaniuk@linaro.org>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/MAINTAINERS b/MAINTAINERS
index dac76e0..ace7d9a 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -634,6 +634,7 @@
 S:	Maintained
 F:	drivers/tee/
 F:	include/tee.h
+F:	include/tee/
 
 UBI
 M:	Kyungmin Park <kmpark@infradead.org>