feat(bl): add interface to query TF-A semantic ver

Adding interface for stand-alone semantic version of TF-A
for exporting to RSS attestation, and potentially other areas
as well.

Signed-off-by: Lauren Wehrmeister <lauren.wehrmeister@arm.com>
Change-Id: Ib4a2c47aa1e42a3b850185e674c90708a05cda53
diff --git a/include/common/bl_common.h b/include/common/bl_common.h
index 3a06cfb..539280e 100644
--- a/include/common/bl_common.h
+++ b/include/common/bl_common.h
@@ -178,6 +178,7 @@
 
 extern const char build_message[];
 extern const char version_string[];
+const char *get_version(void);
 
 void print_entry_point_info(const entry_point_info_t *ep_info);
 uintptr_t page_align(uintptr_t value, unsigned dir);