correct a bug in an ARM codegen testcase

Hi Renato and Anton -
(I'm mailing you based on what I see in CODE_OWNERS.txt.)

Hi Sanjay,

The best thing to do is usually to check on the mailing list, not direct emails.

In llvm/test/CodeGen/ARM/fnegs.ll, we have several different RUN invocations
for llc, but the CHECKs don't match. There is no run that has prefix "NFP0".

I can see...

; RUN: llc -mtriple=arm-eabi -mattr=+neon %s -o - \
; RUN: | FileCheck %s -check-prefix=NFP0

; NFP0-LABEL: test1:
; NFP0: vneg.f32 s{{.*}}, s{{.*}}

etc.

I tracked the bug down to r99570. At that time, "-arm-use-neon-fp" was
removed.

When originally written, the testcase specified "-mattr=+neon,-neonfp".

I don't know enough about ARM and LLVM to know if what was specified back in
2009 is still meaningful. Ie, is the right fix to add the original
"-mattr=+neon,-neonfp" RUN invocation back or something else?

I still don't know what the "bug" is that needs fixing. Can you share
what's going on your side?

cheers,
--renato