coverity: Fix MISRA null pointer violations

Fix code that violates the MISRA rule:
MISRA C-2012 Rule 11.9: Literal "0" shall not be used as
null pointer constant.

The fix explicitly checks whether a pointer is NULL.

Change-Id: Ibc318dc0f464982be9a34783f24ccd1d44800551
Signed-off-by: Zelalem <zelalem.aweke@arm.com>
diff --git a/common/desc_image_load.c b/common/desc_image_load.c
index f2e8f60..b483597 100644
--- a/common/desc_image_load.c
+++ b/common/desc_image_load.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016-2019, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2016-2020, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -301,9 +301,9 @@
 			image_info_t *bl33_image_info;
 		} *v1 = (void *)(uintptr_t)param;
 		assert(v1->h.type == PARAM_BL31);
-		if (bl32_ep_info_out)
+		if (bl32_ep_info_out != NULL)
 			*bl32_ep_info_out = *v1->bl32_ep_info;
-		if (bl33_ep_info_out)
+		if (bl33_ep_info_out != NULL)
 			*bl33_ep_info_out = *v1->bl33_ep_info;
 		return;
 	}
@@ -311,12 +311,12 @@
 
 	assert(v2->h.version == PARAM_VERSION_2);
 	assert(v2->h.type == PARAM_BL_PARAMS);
-	for (node = v2->head; node; node = node->next_params_info) {
+	for (node = v2->head; node != NULL; node = node->next_params_info) {
 		if (node->image_id == BL32_IMAGE_ID)
-			if (bl32_ep_info_out)
+			if (bl32_ep_info_out != NULL)
 				*bl32_ep_info_out = *node->ep_info;
 		if (node->image_id == BL33_IMAGE_ID)
-			if (bl33_ep_info_out)
+			if (bl33_ep_info_out != NULL)
 				*bl33_ep_info_out = *node->ep_info;
 	}
 }