build(corstone1000): rename diphda to corstone1000

diphda platform is now being renamed to corstone1000.
These changes are to replace all the instances and traces
of diphda  corstone1000.

Change-Id: I330f3a112d232b99b4721b6bf0236253b068dbba
Signed-off-by: Arpita S.K <Arpita.S.K@arm.com>
Signed-off-by: Vishnu Banavath <vishnu.banavath@arm.com>
diff --git a/docs/plat/arm/index.rst b/docs/plat/arm/index.rst
index f262dc0..2f68522 100644
--- a/docs/plat/arm/index.rst
+++ b/docs/plat/arm/index.rst
@@ -13,7 +13,7 @@
    arm_fpga/index
    arm-build-options
    morello/index
-   diphda/index
+   corstone1000/index
 
 This chapter holds documentation related to Arm's development platforms,
 including both software models (FVPs) and hardware development boards