Build: Increase manual version of TF-M to v1.8.1

Signed-off-by: Antonio de Angelis <antonio.deangelis@arm.com>
Change-Id: I60b0634e35e3e3c35568de0ebd8b32b5eabceb8b
diff --git a/cmake/version.cmake b/cmake/version.cmake
index 4c1b2ea..b036c97 100644
--- a/cmake/version.cmake
+++ b/cmake/version.cmake
@@ -6,7 +6,7 @@
 #-------------------------------------------------------------------------------
 
 # The 'TFM_VERSION_MANUAL' is used for fallback when Git tags are not available
-set(TFM_VERSION_MANUAL "1.8.0")
+set(TFM_VERSION_MANUAL "1.8.1")
 
 execute_process(COMMAND git describe --tags --always
     WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}