target/arm: Remove local definitions of float constants

target/arm: Remove local definitions of float constants

In several places the target/arm code defines local float constants
for 2, 3 and 1.5, which are also provided by include/fpu/softfloat.h.
Remove the unnecessary local duplicate versions.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20200828183354.27913-2-peter.maydell@linaro.org