ac: replace HAVE_LLVM with LLVM_VERSION_MAJOR for atomic-optimizations

trivial
diff --git a/src/amd/common/ac_llvm_util.c b/src/amd/common/ac_llvm_util.c
index deca5b9..6494267 100644
--- a/src/amd/common/ac_llvm_util.c
+++ b/src/amd/common/ac_llvm_util.c
@@ -63,7 +63,7 @@
 		"mesa",
 		"-simplifycfg-sink-common=false",
 		"-global-isel-abort=2",
-#if HAVE_LLVM >= 0x1000
+#if LLVM_VERSION_MAJOR >= 10
 		/* Atomic optimizations require LLVM 10.0 for gfx10 support. */
 		"-amdgpu-atomic-optimizations=true",
 #endif