linux-user: define missing sparc syscalls

NR_lookup_dcookie, NR_fadvise64, NR_fadvise64_64

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>