Reset EL2 and EL3 configurable controls

This patch resets EL2 and EL3 registers that have architecturally
UNKNOWN values on reset and that also provide EL2/EL3 configuration
and trap controls.

Specifically, the EL2 physical timer is disabled to prevent timer
interrups into EL2 - CNTHP_CTL_EL2 and CNTHP_CTL for AArch64 and AArch32,
respectively.

Additionally, for AArch64, HSTR_EL2 is reset to avoid unexpected traps of
non-secure access to certain system registers at EL1 or lower.

For AArch32, the patch also reverts the reset to SDCR which was
incorrectly added in a previous change.

Change-Id: If00eaa23afa7dd36a922265194ccd6223187414f
Signed-off-by: David Cunado <david.cunado@arm.com>
diff --git a/include/lib/aarch64/arch_helpers.h b/include/lib/aarch64/arch_helpers.h
index 37db031..a013809 100644
--- a/include/lib/aarch64/arch_helpers.h
+++ b/include/lib/aarch64/arch_helpers.h
@@ -280,6 +280,8 @@
 DEFINE_SYSREG_READ_FUNC(ctr_el0)
 
 DEFINE_SYSREG_RW_FUNCS(mdcr_el2)
+DEFINE_SYSREG_RW_FUNCS(hstr_el2)
+DEFINE_SYSREG_RW_FUNCS(cnthp_ctl_el2)
 DEFINE_SYSREG_READ_FUNC(pmcr_el0)
 
 DEFINE_RENAME_SYSREG_RW_FUNCS(icc_sre_el1, ICC_SRE_EL1)