target-arm: VFPv4 implies half-precision extension

target-arm: VFPv4 implies half-precision extension

VFPv4 implies the presence of the half-precision floating point
extension (which is optional in VFPv3). Add this implied rule
to arm_cpu_realizefn() and remove some no-longer-needed explicit
setting of the bit in initfns.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1401458125-27977-5-git-send-email-peter.maydell@linaro.org