Provide cm_get/set_context() for current CPU

All callers of cm_get_context() pass the calling CPU MPIDR to the
function. Providing a specialised version for the current
CPU results in a reduction in code size and better readability.

The current function has been renamed to cm_get_context_by_mpidr()
and the existing name is now used for the current-CPU version.

The same treatment has been done to cm_set_context(), although
only both forms are used at present in the PSCI and TSPD code.

Change-Id: I91cb0c2f7bfcb950a045dbd9ff7595751c0c0ffb
diff --git a/services/std_svc/psci/psci_afflvl_suspend.c b/services/std_svc/psci/psci_afflvl_suspend.c
index 377afdf..a986e5c 100644
--- a/services/std_svc/psci/psci_afflvl_suspend.c
+++ b/services/std_svc/psci/psci_afflvl_suspend.c
@@ -180,7 +180,7 @@
 	 * The EL3 state to PoC since it will be accessed after a
 	 * reset with the caches turned off
 	 */
-	saved_el3_state = get_el3state_ctx(cm_get_context(mpidr, NON_SECURE));
+	saved_el3_state = get_el3state_ctx(cm_get_context(NON_SECURE));
 	flush_dcache_range((uint64_t) saved_el3_state, sizeof(*saved_el3_state));
 
 	/* Set the secure world (EL3) re-entry point after BL1 */
@@ -496,7 +496,6 @@
 	 * structure. The non-secure context should have been
 	 * set on this cpu prior to suspension.
 	 */
-	assert(cm_get_context(mpidr, NON_SECURE));
 	cm_set_next_eret_context(NON_SECURE);
 	cm_init_pcpu_ptr_cache();
 	write_vbar_el3((uint64_t) runtime_exceptions);