feat(fwu): update the URL links for the FWU specification

Update the links for accessing the FWU Multi Bank update specification
to point to the latest revision of the specification.

Change-Id: I25f35556a94ca81ca0a7463aebfcbc2d84595e8f
Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
diff --git a/docs/getting_started/build-options.rst b/docs/getting_started/build-options.rst
index 37545ce..def9fda 100644
--- a/docs/getting_started/build-options.rst
+++ b/docs/getting_started/build-options.rst
@@ -1345,7 +1345,7 @@
 *Copyright (c) 2019-2024, Arm Limited. All rights reserved.*
 
 .. _DEN0115: https://developer.arm.com/docs/den0115/latest
-.. _PSA FW update specification: https://developer.arm.com/documentation/den0118/a/
+.. _PSA FW update specification: https://developer.arm.com/documentation/den0118/latest/
 .. _PSA DRTM specification: https://developer.arm.com/documentation/den0113/a
 .. _GCC: https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html
 .. _Clang: https://clang.llvm.org/docs/DiagnosticsReference.html