[clang] [clang][ARM] Fix warning for using VFP from interrupts. (PR #91870)

[David Spickett via cfe-commits]

DavidSpickett wrote:

Everything LGTM but I'd like someone who works on Arm's downstream compiler to approve. @ostannard perhaps? 

(thanks for your patience @chrisnc)

https://github.com/llvm/llvm-project/pull/91870