fix: split chained assignment between incompatible fn-pointer types

cached_send (send_fn) and cached_recv (recv_fn) differ in their second
parameter (const void* vs void*); chaining the assignment forced an
implicit recv_fn -> send_fn conversion that clang rejects. Split into
two statements to match the line below.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: jbachorik

ddprof-lib/src/main/cpp/libraryPatcher_linux.cpp

@@ -422,7 +422,7 @@ bool LibraryPatcher::patch_socket_functions() {
         cached_write == &NativeSocketSampler::write_hook ||
         cached_read  == &NativeSocketSampler::read_hook) {
       TEST_LOG("patch_socket_functions dlsym returned hook address; refusing to self-reference");
-      cached_send = cached_recv = nullptr;
+      cached_send = nullptr; cached_recv = nullptr;
       cached_write = nullptr; cached_read = nullptr;
       return false;
     }