Docs: Refine tfm_sw_requirement.rst

Simplify the tfm software requirement document and change the document
to 'tfm_getting_started.rst', let it more
suitable for new starter.

Signed-off-by: Summer Qin <summer.qin@arm.com>
Change-Id: I10379aa92ac2c6cd784f0fd1b1b5431243716d74
diff --git a/docs/contributing/contributing_process.rst b/docs/contributing/contributing_process.rst
index 002df7e..8bd7e52 100644
--- a/docs/contributing/contributing_process.rst
+++ b/docs/contributing/contributing_process.rst
@@ -26,7 +26,7 @@
 
   - Clone the TF-M code on your own machine from `TF-M git repository
     <https://git.trustedfirmware.org/TF-M/trusted-firmware-m.git>`_.
-  - Follow the :doc:`SW Requirements </docs/getting_started/tfm_sw_requirement>`,
+  - Follow the :doc:`TF-M getting started </docs/getting_started/tfm_getting_started>`,
     :doc:`Build Instructions </docs/technical_references/instructions/tfm_build_instruction>` and
     :doc:`Coding Guide </docs/contributing/coding_guide>` for the TF-M project.
   - Make your changes in logical chunks to help reviewers. Each commit should