pdr: Document preconditions for trivial accessor functions

Don't force the implementation to handle invalid pointers and convolute
what should be a simple API.

Callers must already be validating this precondition to avoid the
assert() in the implementations. The change just explicitly defines the
requirement.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: I8285c998ed5cd69489f00b3873dadf7901938ace
diff --git a/src/pdr.c b/src/pdr.c
index c350177..3cd0f3a 100644
--- a/src/pdr.c
+++ b/src/pdr.c
@@ -261,7 +261,8 @@
 }
 
 LIBPLDM_ABI_STABLE
-uint32_t pldm_pdr_get_record_handle(const pldm_pdr *repo,
+uint32_t pldm_pdr_get_record_handle(const pldm_pdr *repo
+				    __attribute__((unused)),
 				    const pldm_pdr_record *record)
 {
 	assert(repo != NULL);