Merge pull request #1133 from geesun/qx/fixed_tbbr_doc_ver

docs: Update Trusted Board Boot Requirements document number
diff --git a/docs/firmware-design.rst b/docs/firmware-design.rst
index f28d2f6..e16e9b8 100644
--- a/docs/firmware-design.rst
+++ b/docs/firmware-design.rst
@@ -2431,7 +2431,7 @@
 References
 ----------
 
-.. [#] Trusted Board Boot Requirements CLIENT PDD (ARM DEN 0006B-5). Available
+.. [#] Trusted Board Boot Requirements CLIENT PDD (ARM DEN0006C-1). Available
        under NDA through your ARM account representative.
 .. [#] `Power State Coordination Interface PDD`_
 .. [#] `SMC Calling Convention PDD`_