target/arm: Split out flags setting from vfp compares

target/arm: Split out flags setting from vfp compares

Minimize the code within a macro by splitting out a helper function.
Use deposit32 instead of manual bit manipulation.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20190209033847.9014-9-richard.henderson@linaro.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>