dsp: pdr: Open-code next_container_id() at its callsite

There was only one invocation. Open-code the implementation so its
easier to understand the assertion should never fire.

Change-Id: I8963c3e15afa85f8bc5457b6cd94a272f408b48a
Signed-off-by: Andrew Jeffery <andrew@codeconstruct.com.au>
diff --git a/src/dsp/pdr.c b/src/dsp/pdr.c
index 732a1d6..0f73f02 100644
--- a/src/dsp/pdr.c
+++ b/src/dsp/pdr.c
@@ -461,14 +461,6 @@
 	uint8_t association_type;
 } pldm_entity_node;
 
-LIBPLDM_CC_NONNULL
-static inline uint16_t next_container_id(pldm_entity_association_tree *tree)
-{
-	assert(tree->last_used_container_id != UINT16_MAX);
-
-	return ++tree->last_used_container_id;
-}
-
 LIBPLDM_ABI_STABLE
 pldm_entity pldm_entity_extract(pldm_entity_node *node)
 {
@@ -595,8 +587,11 @@
 			if (container_id != 0xffff) {
 				node->entity.entity_container_id = container_id;
 			} else {
+				/* We will have returned above */
+				assert(tree->last_used_container_id !=
+				       UINT16_MAX);
 				node->entity.entity_container_id =
-					next_container_id(tree);
+					++tree->last_used_container_id;
 			}
 		} else {
 			node->entity.entity_container_id =