refactor(cpufeat): rename ENABLE_SPE_FOR_LOWER_ELS to ENABLE_SPE_FOR_NS

At the moment we hardcode the SPE functionality to be available on the
non-secure side only, by setting MDCR_EL2.E2PB accordingly.

This should be reflected in the feature selection symbol, so rename that
to ENABLE_SPE_FOR_NS, to make it clearer that SPE is not supported in
the secure world.

Change-Id: I3f9b48eab1a45d6ccfcbb9c90a11eeb66867ad9a
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
diff --git a/Makefile b/Makefile
index b9ca664..16279b6 100644
--- a/Makefile
+++ b/Makefile
@@ -1096,7 +1096,7 @@
         ENABLE_RUNTIME_INSTRUMENTATION \
         ENABLE_SME_FOR_NS \
         ENABLE_SME_FOR_SWD \
-        ENABLE_SPE_FOR_LOWER_ELS \
+        ENABLE_SPE_FOR_NS \
         ENABLE_SVE_FOR_NS \
         ENABLE_SVE_FOR_SWD \
         ERROR_DEPRECATED \
@@ -1237,7 +1237,7 @@
         ENABLE_RUNTIME_INSTRUMENTATION \
         ENABLE_SME_FOR_NS \
         ENABLE_SME_FOR_SWD \
-        ENABLE_SPE_FOR_LOWER_ELS \
+        ENABLE_SPE_FOR_NS \
         ENABLE_SVE_FOR_NS \
         ENABLE_SVE_FOR_SWD \
         ENCRYPT_BL31 \