SPM: Ignore empty regions in resource description

Instead of letting the code run until another error is reached, return
early.

Change-Id: I6277a8c65101d3e39b0540099c2a3063584a7dbd
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

services/std_svc/spm/spm_xlat.c

 /*
- * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2018-2019, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -159,6 +159,11 @@ static void map_rdmem(sp_context_t *sp_ctx, struct sp_rd_sect_mem_region *rdmem)
 
 	unsigned int memtype = rdmem->attr & RD_MEM_MASK;
 
+	if (rd_size == 0U) {
+		VERBOSE("Memory region '%s' is empty. Ignored.\n", rdmem->name);
+		return;
+	}
+
 	VERBOSE("Adding memory region '%s'\n", rdmem->name);
 
 	mmap.granularity = REGION_DEFAULT_GRANULARITY;