linux-user: fix emulation of splice syscall The second and fourth argument are in/out parameters, store them back after the syscall. Also, the fourth argument was mishandled, and EFAULT handling was missing. Signed-off-by: Andreas Schwab <schwab@suse.de> Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>