linux-user: Use target abi_int type for pipefd[1] in pipe()

When writing back the fd[1] pipe file handle to emulated userspace
memory, use sizeof(abi_int) as offset insted of the hosts's int type.
There is no functional change in this patch.

Signed-off-by: Helge Deller <deller@gmx.de>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

Message-Id: <YtQ3Id6z8slpVr7r@p100>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>