Fix: fixing coverity issue for SPM Core.

spmd_get_context_by_mpidr was using potentially negative value as an
array index. plat_core_pos_by_mpidr could return -1 on failure which is
utilized by some platforms.
Signed-off-by: Max Shvetsov <maksims.svecovs@arm.com>
Change-Id: I7f8827e77f18da389c9cafdc1fc841aba9f03120

services/std_svc/spmd/spmd_main.c

@@ -46,7 +46,14 @@ static entry_point_info_t *spmc_ep_info;
  ******************************************************************************/
 spmd_spm_core_context_t *spmd_get_context_by_mpidr(uint64_t mpidr)
 {
-	return &spm_core_context[plat_core_pos_by_mpidr(mpidr)];
+	int core_idx = plat_core_pos_by_mpidr(mpidr);
+
+	if (core_idx < 0) {
+		ERROR("Invalid mpidr: %llx, returned ID: %d\n", mpidr, core_idx);
+		panic();
+	}
+
+	return &spm_core_context[core_idx];
 }
 
 /*******************************************************************************