Auto merge of #131871 - RalfJung:x86-32-float, r=workingjubilee

x86-32 float return for 'Rust' ABI: treat all float types consistently

This helps with rust-lang/rust#131819: for our own ABI on x86-32, we want to *never* use the float registers. The previous logic only considered F32 and F64, but skipped F16 and F128. So I made the logic just apply to all float types.

try-job: i686-gnu
try-job: i686-gnu-nopt

Author: bors