Setup VBAR_EL3 incrementally

This patch ensures that VBAR_EL3 points to the simple stack-less
'early_exceptions' when the C runtime stack is not correctly setup to
use the more complex 'runtime_exceptions'. It is initialised to
'runtime_exceptions' once this is done.

This patch also moves all exception vectors into a '.vectors' section
and modifies linker scripts to place all such sections together. This
will minimize space wastage from alignment restrictions.

Change-Id: I8c3e596ea3412c8bd582af9e8d622bb1cb2e049d
diff --git a/bl31/aarch64/bl31_entrypoint.S b/bl31/aarch64/bl31_entrypoint.S
index 57f6551..cd0c023 100644
--- a/bl31/aarch64/bl31_entrypoint.S
+++ b/bl31/aarch64/bl31_entrypoint.S
@@ -58,7 +58,7 @@
 	 * Set the exception vector to something sane.
 	 * ---------------------------------------------
 	 */
-	adr	x1, runtime_exceptions
+	adr	x1, early_exceptions
 	msr	vbar_el3, x1
 
 	/* ---------------------------------------------------------------------
@@ -155,6 +155,14 @@
 	bl	platform_set_stack
 
 	/* ---------------------------------------------
+	 * Use the more complex exception vectors now
+	 * the stacks are setup.
+	 * ---------------------------------------------
+	 */
+	adr	x1, runtime_exceptions
+	msr	vbar_el3, x1
+
+	/* ---------------------------------------------
 	 * Use SP_EL0 to initialize BL31. It allows us
 	 * to jump to the next image without having to
 	 * come back here to ensure all of the stack's