docs: simplify 'cd'ing into TF-M folder

Currently docs use two 'cd' commands to move to the TF-M
folder (1. move to base folder 2. move to TF-M folder). This patch
simplifies to a single 'cd' command, moving directly to TF-M base
folder.

Signed-off-by: Leonardo Sandoval <leonardo.sandoval@linaro.org>
Change-Id: I8d67b73d749962672aca4b351ae5b18efb38283e
diff --git a/docs/getting_started/tfm_build_instruction_iar.rst b/docs/getting_started/tfm_build_instruction_iar.rst
index 2ee9196..a320488 100644
--- a/docs/getting_started/tfm_build_instruction_iar.rst
+++ b/docs/getting_started/tfm_build_instruction_iar.rst
@@ -27,8 +27,7 @@
 ====================================================
 .. code-block:: bash
 
-    cd <base folder>
-    cd trusted-firmware-m
+    cd <TF-M base folder>
     cmake -S . -B cmake_build -DTFM_PLATFORM=mps2/an521 -DTFM_TOOLCHAIN_FILE=toolchain_IARARM.cmake
     cmake --build cmake_build -- install
 
@@ -36,8 +35,7 @@
 
 .. code-block:: bash
 
-    cd <base folder>
-    cd trusted-firmware-m
+    cd <TF-M base folder>
     mkdir cmake_build
     cd cmake_build
     cmake .. -DTFM_PLATFORM=mps2/an521 -DTFM_TOOLCHAIN_FILE=../toolchain_IARARM.cmake
@@ -48,8 +46,7 @@
 
 .. code-block:: bash
 
-    cd <base folder>
-    cd trusted-firmware-m
+    cd <TF-M base folder>
     cmake -S . -B cmake_build -DTFM_PLATFORM=mps2/an521 -DTFM_TOOLCHAIN_FILE=toolchain_IARARM.cmake -DTEST_S=ON -DTEST_NS=ON
     cmake --build cmake_build -- install
 
@@ -57,8 +54,7 @@
 
 .. code-block:: bash
 
-    cd <base folder>
-    cd trusted-firmware-m
+    cd <TF-M base folder>
     mkdir cmake_build
     cd cmake_build
     cmake .. -DTFM_PLATFORM=mps2/an521 -DTFM_TOOLCHAIN_FILE=../toolchain_IARARM.cmake -DTEST_S=ON -DTEST_NS=ON