refactor(smccc): move debugfs to vendor el3 calls

Move debugfs to Vendor-Specific EL3 Monitor Service Calls.
Function Identifier for Vendor-Specific EL3 Monitor Service is '7' and
allocated subranges of Function identifiers to different services are:

0x87000000-0x8700FFFF-SMC32: Vendor-Specific EL3 Monitor Service Calls
0xC7000000-0xC700FFFF-SMC64: Vendor-Specific EL3 Monitor Service Calls

Amend Debugfs FID's to use this range and id.

Add a deprecation notice to inform debugfs moved from arm-sip range to
Vendor-Specific EL3 range. Debugfs support from arm-sip range will be
removed and will not be available after TF-A 2.12 release.

Reference to debugfs component level documentation:
https://trustedfirmware-a.readthedocs.io/en/latest/components/debugfs-design.html#overview

Change-Id: I97a50170178f361f70c95ed0049bc4e278de59d7
Signed-off-by: Govindraj Raja <govindraj.raja@arm.com>
diff --git a/docs/components/ven-el3-service.rst b/docs/components/ven-el3-service.rst
index fe83845..fc9f13c 100644
--- a/docs/components/ven-el3-service.rst
+++ b/docs/components/ven-el3-service.rst
@@ -19,9 +19,26 @@
 | 0xC7000000 - 0xC700FFFF   | SMC64: Vendor Specific EL3 Monitor Service Calls |
 +---------------------------+--------------------------------------------------+
 
+Vendor-specific EL3 monitor services are as follows:
+
++-----------------------------------+-----------------------+---------------------------------------------+
+| SMC Function Identifier           | Service Type          | FID's Usage                                 |
++===================================+=======================+=============================================+
+| 0x87000010 - 0x8700001F (SMC32)   | DebugFS Interface     | | 0 - 11 are in use                         |
++-----------------------------------+                       | | 12 - 15 are reserved for future expansion |
+| 0xC7000010 - 0xC700001F (SMC64)   |                       |                                             |
++-----------------------------------+-----------------------+---------------------------------------------+
+
 Source definitions for vendor-specific EL3 Monitor Service Calls are located in
 the ``ven_el3_svc.h`` header file.
 
+
+DebugFS interface
+-----------------
+
+The optional DebugFS interface is accessed through Vendor specific EL3 service. Refer
+to :ref:`DebugFS interface` documentation for further details and usage.
+
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