board/rdn1edge: rename sgiclarka to rdn1edge

Replace all usage of 'sgiclark' with 'rdn1e1edge' and 'sgiclarka' with
'rdn1edge' as per the updated product names.

Change-Id: Idbc157c73477ec32f507ba2d4a4e907d8813374c
Signed-off-by: Chandni Cherukuri <chandni.cherukuri@arm.com>
diff --git a/readme.rst b/readme.rst
index deca2d2..2d7af75 100644
--- a/readme.rst
+++ b/readme.rst
@@ -194,7 +194,7 @@
 
 -  Allwinner sun50i_64 and sun50i_h6
 -  Amlogic Meson S905 (GXBB)
--  Arm SGI-575, SGI Clark.A, SGI Clark.H and SGM-775
+-  Arm SGI-575, RDN1Edge, SGI Clark.H and SGM-775
 -  Arm Neoverse N1 System Development Platform
 -  HiKey, HiKey960 and Poplar boards
 -  Marvell Armada 3700 and 8K