Build: Restructure Musca-B1 folders

Original musca_b1 platform is renamed to musca_b1/sse_200, and
musca_b1_secure_enclave is renamed to musca_b1/secure_enclave.

Change-Id: If05f1878cff3808ec95e207abe4a0a433998523c
Signed-off-by: Gabor Abonyi <gabor.abonyi@arm.com>
Signed-off-by: Mark Horvath <mark.horvath@arm.com>
diff --git a/docs/introduction/readme.rst b/docs/introduction/readme.rst
index e867ba3..2e07c11 100644
--- a/docs/introduction/readme.rst
+++ b/docs/introduction/readme.rst
@@ -162,7 +162,7 @@
 
     - Secure Enclave system:
 
-        - :doc:`Musca-B1 Secure Enclave. </platform/ext/target/musca_b1_secure_enclave/readme>`
+        - :doc:`Musca-B1 Secure Enclave. </platform/ext/target/musca_b1/secure_enclave/readme>`
 
 The document :doc:`Platform Deprecation and Removal </docs/contributing/platform_deprecation>`
 lists the deprecated platforms planned to be removed from upstream.