linux-user: Make sure NWFPE code is 32 bit ARM only

On ARM, linux-user emulation includes NWFPE support for emulating the
ancient FPA floating point coprocessor. This has long since been
superseded by VFP and is only required for legacy binaries. The
AArch64 linux-user target doesn't compile in NWFPE support, so make
sure the relevant code is protected by suitable ifdefs.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1378235544-22290-18-git-send-email-peter.maydell@linaro.org
