LLVM_FALLTHROUGH => [[fallthrough]]. NFC

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D150996
diff --git a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
index 31d6d97..3b10a27 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
@@ -2529,7 +2529,7 @@
       return 2 * LT.first;
     if (!Ty->getScalarType()->isFP128Ty())
       return LT.first;
-    LLVM_FALLTHROUGH;
+    [[fallthrough]];
   case ISD::FMUL:
   case ISD::FDIV:
     // These nodes are marked as 'custom' just to lower them to SVE.