Update link to SMCCC specification

The feature overview page points to the revision B published in November
2016, update the link to point to the latest version (currently 1.2
published in March 2020).

Remove the link from implementing-tests.rst, as it is not referenced in
the page.

Change-Id: I9ac12eba39d33914bfc2474a5a9851e628010349
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
diff --git a/docs/about/features.rst b/docs/about/features.rst
index b6fc2d0..dbaec12 100644
--- a/docs/about/features.rst
+++ b/docs/about/features.rst
@@ -42,9 +42,9 @@
 
 --------------
 
-*Copyright (c) 2019, Arm Limited. All rights reserved.*
+*Copyright (c) 2019-2020, Arm Limited. All rights reserved.*
 
-.. _SMC Calling Convention: http://infocenter.arm.com/help/topic/com.arm.doc.den0028b/ARM_DEN0028B_SMC_Calling_Convention.pdf
+.. _SMC Calling Convention: https://developer.arm.com/docs/den0028/latest
 .. _Power State Coordination Interface (PSCI): PSCI_
 .. _PSCI: http://infocenter.arm.com/help/topic/com.arm.doc.den0022d/Power_State_Coordination_Interface_PDD_v1_1_DEN0022D.pdf
 .. _Software Delegated Exception Interface (SDEI): SDEI_
diff --git a/docs/implementing-tests.rst b/docs/implementing-tests.rst
index e72a277..8df667c 100644
--- a/docs/implementing-tests.rst
+++ b/docs/implementing-tests.rst
@@ -110,7 +110,4 @@
 
 --------------
 
-*Copyright (c) 2018-2019, Arm Limited. All rights reserved.*
-
-.. _SMC Calling Convention: SMCCC_
-.. _SMCCC: http://infocenter.arm.com/help/topic/com.arm.doc.den0028b/ARM_DEN0028B_SMC_Calling_Convention.pdf
+*Copyright (c) 2018-2020, Arm Limited. All rights reserved.*