Initialise CPU contexts from entry_point_info

Consolidate all BL3-1 CPU context initialization for cold boot, PSCI
and SPDs into two functions:
*  The first uses entry_point_info to initialize the relevant
   cpu_context for first entry into a lower exception level on a CPU
*  The second populates the EL1 and EL2 system registers as needed
   from the cpu_context to ensure correct entry into the lower EL

This patch alters the way that BL3-1 determines which exception level
is used when first entering EL1 or EL2 during cold boot - this is now
fully determined by the SPSR value in the entry_point_info for BL3-3,
as set up by the platform code in BL2 (or otherwise provided to BL3-1).

In the situation that EL1 (or svc mode) is selected for a processor
that supports EL2, the context management code will now configure all
essential EL2 register state to ensure correct execution of EL1. This
allows the platform code to run non-secure EL1 payloads directly
without requiring a small EL2 stub or OS loader.

Change-Id: If9fbb2417e82d2226e47568203d5a369f39d3b0f
diff --git a/services/std_svc/psci/psci_setup.c b/services/std_svc/psci/psci_setup.c
index 015beab..af82150 100644
--- a/services/std_svc/psci/psci_setup.c
+++ b/services/std_svc/psci/psci_setup.c
@@ -59,7 +59,7 @@
 
 /*******************************************************************************
  * 'psci_ns_einfo_idx' keeps track of the next free index in the
- * 'psci_ns_entry_info' & 'psci_suspend_context' arrays.
+ * 'psci_suspend_context' arrays.
  ******************************************************************************/
 static unsigned int psci_ns_einfo_idx;