feat(sve): enable SVE for the secure world

Enables SVE support for the secure world via ENABLE_SVE_FOR_SWD.
ENABLE_SVE_FOR_SWD defaults to 0 and has to be explicitly set by the
platform. SVE is configured during initial setup and then uses EL3
context save/restore routine to switch between SVE configurations for
different contexts.
Reset value of CPTR_EL3 changed to be most restrictive by default.

Signed-off-by: Max Shvetsov <maksims.svecovs@arm.com>
Change-Id: I889fbbc2e435435d66779b73a2d90d1188bf4116
diff --git a/make_helpers/defaults.mk b/make_helpers/defaults.mk
index 0433123..b2d1ee2 100644
--- a/make_helpers/defaults.mk
+++ b/make_helpers/defaults.mk
@@ -299,13 +299,15 @@
 ENABLE_AMU			:= 0
 AMU_RESTRICT_COUNTERS		:= 0
 
-# By default, enable Scalable Vector Extension if implemented for Non-secure
+# By default, enable Scalable Vector Extension if implemented only for Non-secure
 # lower ELs
 # Note SVE is only supported on AArch64 - therefore do not enable in AArch32
 ifneq (${ARCH},aarch32)
     ENABLE_SVE_FOR_NS		:= 1
+    ENABLE_SVE_FOR_SWD		:= 0
 else
     override ENABLE_SVE_FOR_NS	:= 0
+    override ENABLE_SVE_FOR_SWD  := 0
 endif
 
 SANITIZE_UB := off