CSS: Changes for SDS framework

This patch does the required changes to enable CSS platforms
to build and use the SDS framework. Since SDS is always coupled with
SCMI protocol, the preexisting SCMI build flag is now renamed to
`CSS_USE_SCMI_SDS_DRIVER` which will enable both SCMI and SDS on
CSS platforms. Also some of the workarounds applied for SCMI are
now removed with SDS in place.

Change-Id: I94e8b93f05e3fe95e475c5501c25bec052588a9c
Signed-off-by: Soby Mathew <soby.mathew@arm.com>
diff --git a/docs/user-guide.rst b/docs/user-guide.rst
index 043af63..6031dd9 100644
--- a/docs/user-guide.rst
+++ b/docs/user-guide.rst
@@ -669,9 +669,10 @@
    SCP\_BL2U to the FIP and FWU\_FIP respectively, and enables them to be loaded
    during boot. Default is 1.
 
--  ``CSS_USE_SCMI_DRIVER``: Boolean flag which selects SCMI driver instead of
-   SCPI driver for communicating with the SCP during power management operations.
-   If this option is set to 1, then SCMI driver will be used. Default is 0.
+-  ``CSS_USE_SCMI_SDS_DRIVER``: Boolean flag which selects SCMI/SDS drivers
+   instead of SCPI/BOM driver for communicating with the SCP during power
+   management operations and for SCP RAM Firmware transfer. If this option
+   is set to 1, then SCMI/SDS drivers will be used. Default is 0.
 
 ARM FVP platform specific build options
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^