docs: tfm_build_instruction.rst: fix for STM platform build

Change-Id: I26b21fc041ee56109548b0e63d7ec64a8a6cdcbe
diff --git a/docs/getting_started/tfm_build_instruction.rst b/docs/getting_started/tfm_build_instruction.rst
index 8a0198a..b96741c 100644
--- a/docs/getting_started/tfm_build_instruction.rst
+++ b/docs/getting_started/tfm_build_instruction.rst
@@ -261,7 +261,7 @@
             ``-DTARGET_PLATFORM=STM_DISCO_L562QE``
             See :doc:`STM32L5xx platform specifics </platform/ext/target/stm/stm32l5xx/readme>`
           - NUCLEO_L552ZE_Q (Cortex-M33 STM32L552)
-            ``-DTARGET_PLATFORM=SSTM_NUCLEO_L552ZE_Q``
+            ``-DTARGET_PLATFORM=STM_NUCLEO_L552ZE_Q``
             See :doc:`STM32L5xx platform specifics </platform/ext/target/stm/stm32l5xx/readme>`
 
    * - -DCOMPILER=<compiler name>