8251462: Simplify compilation policy

Reviewed-by: cjplummer, kvn

src/hotspot/share/gc/shared/threadLocalAllocBuffer.cpp

@@ -252,7 +252,7 @@ void ThreadLocalAllocBuffer::startup_initialization() {
   // If the C2 compiler is not present, no space is reserved.
 
   // +1 for rounding up to next cache line, +1 to be safe
-  if (is_server_compilation_mode_vm()) {
+  if (CompilerConfig::is_c2_or_jvmci_compiler_enabled()) {
     int lines =  MAX2(AllocatePrefetchLines, AllocateInstancePrefetchLines) + 2;
     _reserve_for_allocation_prefetch = (AllocatePrefetchDistance + AllocatePrefetchStepSize * lines) /
                                        (int)HeapWordSize;