aarch64: Enable Statistical Profiling Extensions for lower ELs

SPE is only supported in non-secure state.  Accesses to SPE specific
registers from SEL1 will trap to EL3.  During a world switch, before
`TTBR` is modified the SPE profiling buffers are drained.  This is to
avoid a potential invalid memory access in SEL1.

SPE is architecturally specified only for AArch64.

Change-Id: I04a96427d9f9d586c331913d815fdc726855f6b0
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>
diff --git a/plat/arm/board/fvp/fvp_pm.c b/plat/arm/board/fvp/fvp_pm.c
index f4df658..e39a4d5 100644
--- a/plat/arm/board/fvp/fvp_pm.c
+++ b/plat/arm/board/fvp/fvp_pm.c
@@ -48,6 +48,14 @@
 {
 	uint64_t mpidr = read_mpidr_el1();
 
+#if ENABLE_SPE_FOR_LOWER_ELS
+	/*
+	 * On power down we need to disable statistical profiling extensions
+	 * before exiting coherency.
+	 */
+	arm_disable_spe();
+#endif
+
 	/* Disable coherency if this cluster is to be turned off */
 	fvp_interconnect_disable();