target/arm: Rename neon_load_reg32 to vfp_load_reg32

The only uses of this function are for loading VFP
single-precision values, and nothing to do with NEON.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20201030022618.785675-8-richard.henderson@linaro.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>