docs: deletion of a few deprecated platforms not yet confirmed

Updated the 'Deprecated Platforms' table to reflect that the
deletion of sgi575 and rdn1Edge is still unconfirmed.

Change-Id: Ie8e8af55a735f624f5ee604d75bb497d870620cd
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
diff --git a/docs/plat/index.rst b/docs/plat/index.rst
index fc3effd..f135ca2 100644
--- a/docs/plat/index.rst
+++ b/docs/plat/index.rst
@@ -73,9 +73,9 @@
 +----------------+----------------+--------------------+--------------------+
 |    mt6795      |      MTK       |        2.5         |       2.7          |
 +----------------+----------------+--------------------+--------------------+
-|    sgi575      |      Arm       |        2.8         |       2.10         |
+|    sgi575      |      Arm       |        2.8         |       TBD          |
 +----------------+----------------+--------------------+--------------------+
-|    rdn1edge    |      Arm       |        2.8         |       2.10         |
+|    rdn1edge    |      Arm       |        2.8         |       TBD          |
 +----------------+----------------+--------------------+--------------------+
 |    tc0         |      Arm       |        2.8         |       2.10         |
 +----------------+----------------+--------------------+--------------------+