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/tfm_design_proposal_process.rst b/docs/contributing/tfm_design_proposal_process.rst
index 49ff7e7..0c10b7b 100644
--- a/docs/contributing/tfm_design_proposal_process.rst
+++ b/docs/contributing/tfm_design_proposal_process.rst
@@ -69,8 +69,8 @@
 available locally. Setting up the documentation tools will allow pre-viewing the
 documentation file in preparation.
 For information on what tools are needed please refer to
-:doc:`sw requirements </docs/getting_started/tfm_sw_requirement>`. To see how to get
-a local copy of the TF-M repository please see
+:doc:`TF-M getting started </docs/getting_started/tfm_getting_started>`. To see
+how to get a local copy of the TF-M repository please see
 :doc:`build instructions </docs/technical_references/instructions/tfm_build_instruction>`
 
 Process steps