clang-tidy: Fix clang-diagnostic-strict-prototypes diagnostics

Produces output such as:

```
/usr/bin/clang-tidy -checks=-*, bugprone-branch-clone -export-fixes /tmp/tmpjjns4w4i/tmp2vh08b10.yaml -p=build /mnt/host/andrew/src/openbmc/libpldm/src/platform.c
/mnt/host/andrew/src/openbmc/libpldm/build/../include/libpldm/pdr.h:35:24: error: a function declaration without a prototype is deprecated in all versions of C [clang-diagnostic-strict-prototypes]
pldm_pdr *pldm_pdr_init();
                       ^
                        void
```

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: Ib9b679682cc25b8c1b294d2be856031f77d755d9
diff --git a/include/libpldm/bios_table.h b/include/libpldm/bios_table.h
index f4796aa..7ec73c8 100644
--- a/include/libpldm/bios_table.h
+++ b/include/libpldm/bios_table.h
@@ -450,7 +450,7 @@
 /** @brief Get length that an attribute entry(type: integer) will take
  *  @return The length that an entry(type: integer) will take
  */
-size_t pldm_bios_table_attr_entry_integer_encode_length();
+size_t pldm_bios_table_attr_entry_integer_encode_length(void);
 
 /** @brief Create an entry of BIOS Attribute Table (type: integer)
  *  @param[out] entry - Pointer to a buffer to create an entry
@@ -617,7 +617,7 @@
 /** @brief Get length that an attribute value entry(type: integer) will take
  *  @return The length that an entry(type: integer) will take
  */
-size_t pldm_bios_table_attr_value_entry_encode_integer_length();
+size_t pldm_bios_table_attr_value_entry_encode_integer_length(void);
 
 /** @brief Create an attribute value entry(type: integer)
  *  @param[out] entry - Pointer to bios attribute value entry
diff --git a/include/libpldm/pdr.h b/include/libpldm/pdr.h
index 671b726..09b376a 100644
--- a/include/libpldm/pdr.h
+++ b/include/libpldm/pdr.h
@@ -32,7 +32,7 @@
  *  for PDRs received by other entities) and can associate the returned handle
  *  to a PLDM terminus id.
  */
-pldm_pdr *pldm_pdr_init();
+pldm_pdr *pldm_pdr_init(void);
 
 /** @brief Destroy a PDR repository (and free up associated resources)
  *
@@ -239,7 +239,7 @@
  *  @return opaque pointer that acts as a handle to the tree; NULL if no
  *  tree could be created
  */
-pldm_entity_association_tree *pldm_entity_association_tree_init();
+pldm_entity_association_tree *pldm_entity_association_tree_init(void);
 
 /** @brief Add an entity into the entity association tree
  *
diff --git a/include/libpldm/requester/pldm.h b/include/libpldm/requester/pldm.h
index 9c5c71e..e0f092f 100644
--- a/include/libpldm/requester/pldm.h
+++ b/include/libpldm/requester/pldm.h
@@ -29,7 +29,7 @@
  *
  * @return fd on success, pldm_requester_rc_t on error (errno may be set)
  */
-pldm_requester_rc_t pldm_open();
+pldm_requester_rc_t pldm_open(void);
 
 /**
  * @brief Send a PLDM request message. Wait for corresponding response message,