Simplify management of SCTLR_EL3 and SCTLR_EL1

This patch reworks the manner in which the M,A, C, SA, I, WXN & EE bits of
SCTLR_EL3 & SCTLR_EL1 are managed. The EE bit is cleared immediately after reset
in EL3. The I, A and SA bits are set next in EL3 and immediately upon entry in
S-EL1. These bits are no longer managed in the blX_arch_setup() functions. They
do not have to be saved and restored either. The M, WXN and optionally the C
bit are set in the enable_mmu_elX() function. This is done during both the warm
and cold boot paths.

Fixes ARM-software/tf-issues#226

Change-Id: Ie894d1a07b8697c116960d858cd138c50bc7a069
diff --git a/bl2/aarch64/bl2_entrypoint.S b/bl2/aarch64/bl2_entrypoint.S
index c615baf..6fcd040 100644
--- a/bl2/aarch64/bl2_entrypoint.S
+++ b/bl2/aarch64/bl2_entrypoint.S
@@ -65,11 +65,13 @@
 	msr	vbar_el1, x0
 
 	/* ---------------------------------------------
-	 * Enable the instruction cache.
+	 * Enable the instruction cache, stack pointer
+	 * and data access alignment checks
 	 * ---------------------------------------------
 	 */
+	mov	x1, #(SCTLR_I_BIT | SCTLR_A_BIT | SCTLR_SA_BIT)
 	mrs	x0, sctlr_el1
-	orr	x0, x0, #SCTLR_I_BIT
+	orr	x0, x0, x1
 	msr	sctlr_el1, x0
 	isb