Make sure rxtx buffers provided in PM are of same size

SPM/hafnium currently allows only same size rx/tx buffers, if different
sizes are provided in Partition's manifest throw an error.
Also, add a unit test to verify it.

Signed-off-by: Manish Pandey <manish.pandey2@arm.com>
Change-Id: I8bab13375b8f62b60caea6384fcd4125fc9eedb0
diff --git a/inc/hf/manifest.h b/inc/hf/manifest.h
index dc4b7c7..3e9eaf4 100644
--- a/inc/hf/manifest.h
+++ b/inc/hf/manifest.h
@@ -228,6 +228,7 @@
 	MANIFEST_ERROR_MALFORMED_BOOLEAN,
 	MANIFEST_ERROR_MEMORY_REGION_NODE_EMPTY,
 	MANIFEST_ERROR_DEVICE_REGION_NODE_EMPTY,
+	MANIFEST_ERROR_RXTX_SIZE_MISMATCH,
 };
 
 enum manifest_return_code manifest_init(struct mm_stage1_locked stage1_locked,